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*« • 


:.. ! * . 

Third Edition— Revised iiCitfr.BjiLiARGED 

•**.*» a 


Calculating the Dimensions of Worm Gearing, by Ralph 
E. Flanders 3 

Hobs for Worm-Gears, by John Edgar - - - 11 

Suggested Refinement in the Robbing of Worm-Wheels, 
by Ralph E. Flanders 15 

The Location of the Pitch Circle in Worm Gearing, by 
Oscar E. Perrigo, John Edgar and Ralph E. 
Flanders 18 

The Hindley Worm and Gear, by John Edgar - - 31 

The Design of Self-Locking Worm-Geai-s, by C. F. Blake 39 

Copyright. 1010. The Industrial Vwhu. PuhlishorH of Maciiinkkt. 
40-55 I^fayctte Street, New York City 






ft 1914 L 


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•« I • 

•• • ••• 

• • • • 

» •• • • 
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• • • • 

• • • -•• 


• • • • •• • • 

• • •• •••••••< 



The present chapter contains a compilation of rules for the caicula- 
Uon of the dimensions of worm eeartng, expressed with as much sim- 
pllcity and clearness as possible. No attempt has been made to give 
rules for estimating the strength or durability of worm gearing, 
although the question of durability, especially, Is the determining fac- 
tor ]n the design of worm gearing. It the worm and wheel are bo 
proportioned as to have a reasonably long life under normal working 
condltlonB, It may be taken for;, gp^t^; that _tt|s tA^t^ , are strong 
enough for the load they have to ^ft.J, Rd'^mpte ^^Ve ever been 
proposed for proportioning worm gep.rln^,W suit fhfi'sfervlce It Is 



dciignod for. Judgment and experience are about the only factors the 
dvigner has for guidance. In Europe, a number of builders are regu- 
larly manufacturing worm drives, guaranteed tor a given horse-power 
at a Blven speed. The dimensions of these drives are not made pub- 
lic, however; they would doubtless be of great value for purposes of 
ctmiparlson if they could be obtained. In the absence of these or other 
practical data, this phase of the subject has. of necessity, not been 
entered upon. 

Daflnltlons and Bulas for DlmenBlone of the Worm 
In giving names to the dimensions of the worm, there Is one point 
In which there la sometimes confusion. This relates to the distinction 
between the terms "pttrh" and lead." In the following we will 
■dbera U) the nomenclature Indicated In Pig. 1. Here are shown three 
wonns, the first single-threaded, the second double-threaded, and the 

, AufnRt, lOUT. 


last trlplft-threaded. As shown, the word "lead" la asBunied to m«ui 
tbe distance which a given thread advaDces. in one revolution of tb« 
worm, while by "pitch," or more strictly, '■linear pitch," we mean the 
distance between the centers of two adjacent threads. As may be 
clearly seen, the lead and linear pitch are equal for a single-threaded 
worm. For a double-threaded worm the lead Is twice the linear pitch, 
and for a triple-threaded worm it Is three times the linear pitch. From 
this we have: 

Rule 1. To find the lead of a worm, multiply the linear plich by the 
number of threadi. 

It Is understood, of course, that by the number of threads is meant, 
not the number of threads per Inch, but the number of threads in the 
whole worm— one, If It la single-threaded, four, if It la quadruplft- 
threaded, etc. Rule I may be transposed to read as follows: 

Role 2. To find the linear pitch of a uiorm. divide the lead by the 
number of thread*. 

The standard fom, of ^om.U><:ead. measured In an axial aection 

as shown in Fig. 2, has the same dimensions as the standard form of 
Involute rack tooth of the same linear or circular pitch. It Is not of 
exactly the same shape, however, not being rounded at the top, nor 
provided with flilets. The thread la cut with a straight-sided tool, 
having a square, flat end. The sides have an Inclination with each 
other of 29 degrees, or l4Vj degrees with the center line. The follow* 
tng rulea give the dimensions of the teeth In an axial aectlbn for 
various linear pitches. For nomenclature, see Fig. 2. 

Rvi.r. 3. To find the whole depth of the worm tooth, multiply the 
linear pitch by 0.6S6S. 

Rule 4. To find the width of the thread tool at the end, mulHpIy 
the linear piteh by 0.31. 

RvLR 5. To find the addendum, or height of tcorm tooth abore tlu 
pilch line, multiply the linear pitch by 0.31S3. 

Rti.K 6. To find the outtide diameter of the worm, add together 
the pitch diameter and twice the addendum. 


Rule T. To Jlnd the pitch diameter of the worm, subtract ttoice 
the addendum Jram the outaide diameler. 

Rdix 8. To flnd the bottom diameter of the worm, subtract twice 
the whole depth of tooth from the outside dianteler. 

Rule 9. To find the helix angle of the wornt and the gashing angle 
of the worm^ioheel tooth, multiplj/ fftc pitch diameter of the worm by 
3.1416. and divide the product by the lead; the guotient is the cotangent 
of the tooth angle of the worm. 

Sulei for DlmeDSlonliig the Wonn-Wlieel 

Tbe dlmenaloDB of the worm-wlieel, named In the dlaKram shown In 
Fig. 3, are derived from tbe number of teeth determined upon for It, 

and tbe dimensions of tbe worm with which It la to meah. The fol- 
lowing mles ma; be used : 

Role JO. To find the pitch diameter of the worm-wheel, multiply 
the number of teeth in the wheel by the linear pitch of the worm, and 
divide ttie product by 3.1416. 

Rdle 11. To find the thjoat diameter of the worm-wheel, add twice 
the addendum of the wortr. tooth to the pitch diameter of the worm 


Rule 12. To find the radius of curvature of the worm-wheel throat, 
subtract twice the addendum of the worm tooth from half the outside 
diameter of the worm. 

The face angle of the wheel Is arbitrarily selected; 60 degrees is a 
good angle, but it may be made as high as 80 or even 90 degrees, 
though there is little advantage in carrying the gear around so great 
a portion of the circumference of the worip, especially in steep pitches. 

Rule 13. To find the diameter of the worm-wheel to sharp comers, 
multiply the throat radius hy the cosine of half the face angle, sub* 
tract this quantity from the throat radius, multiply the remainder 
by 2. and add the product to the throat diameter of the wormrwheel. 

If the sharp corners are flattened a trifle at the tops, as shown in 
Figs. 3 and 5, this dimension need not be figured, "trimmed diameter" 
being easily scaled from an accurate drawing of the gear. 

There is a simple rule which, rightly understood, may be used for 
obtaining the velocity ratio of a pair of gears of any form, whether 
spur, spiral, bevel, or worm. The number of teeth of the driven gear, 
divided by the number of teeth of the driver, will give the velocity 
ratio. For worm gearing this rule takes the following form: 

Rule 14. To find the velocity ratio of a v>orm and worm-^vheel, 
divide the number of teeth in the wheel by the number of threads in 
the worm. 

Be sure that the proper meaning is attached to the phrase "number 
of threads" as explained before under Rule 1. The revolutions per 
minute of the worm, divided by the velocity ratio, gives the revolu- 
tions per minute of the worm-wheel. 

Rule 15. To find the distance between the center of the worm- 
wheel and the center of the worm, add together the pitch diameter of 
the worm and the pitch diameter of the worm-wheel, and divide the 
sum by 2. 

Rule 16. To find the pitch diameter of the worms, subtract the pitch 
diameter of the worm-wheel from twice the center distance. 

The worm should be long enough to allow the wheel to act on it as 
far as it will. The length of the worm required for this may be scaled 
from a carefully-made drawing, or it may be calculated by the follow- 
ing rule: 

Rule 17. To find the minimum length of worm for complete action 
with the worm-wheel, subtract four times the addendum of the worm 
thread from the throat diameter of the wheel, square the remainder, 
and subtract the result from the square of the throat diameter of the 
wheel. The square root of the result is the minimum length of worm 

The length of the worm should ordinarily be longer than the dimen- 
sion thus found. Hobs, particularly, should be long enough for the 
largest wheels they are ever likely to be called upon to cut. 

Departures trom. the Above Rules 

The throat diameter of the wheel and the center distance may have 
to be altered in some cases from the figures given by the preceding 


The pitch diameter of the worm-wheel by Rule 10 is found to be 

32 X % 

= 7.6394 inches. 


The pitch diameter of the worm by Rule 16 is found to be 

(2 X 5) — 7.6394 = 2.3606 inches. 

The addendum of the worm thread by Rule 5 is found to be 

0.3183 X % = 0.2387 inch. 

The outside diameter of the worm by Rule 6 is found to be 

2.3606 -f- (2 X 0.2387) = 2.8380 inches. 

For transmission gearing the angle of inclination of the worm thread 
should be not less than 18 degrees or thereabouts, and the nearer 30 or 
even 40 degrees it is. the more efficient will it be. From Rule 1 we 
find the lead to be 4 x % = 3 Inches. 

The helix angle of the worm thread is found from Rule 9, 2.3606 X 
8.1416 -J- 3 = 2.4722 = cot. 22 degrees, approximately. Tills angle will 
give fairly satisfactory results. The calculations are not carried any 
further with this problem, whose other dimensions are determined 
from those just found. In the following case, however, all the calcu- 
lations are made. 

For a second problem let it be required to design worm feed gearing 
for a machine to utilize a hob already in stock. This hob is double- 
threaded, % inch linear pitch, and 2i^ inches diameter. The center 
distance of the gearing is immaterial, but it is decided that the worm- 
wheel ought to have about 45 teeth to bring the ratio right. The only 
calculations made are those necessary for the dimensions which would 
appear on the shop drawing. 

To find the lead, use Rule 1 : 0.5 x 2 = 1.0 inch. 

To find the whole depth of the worm tooth, use Rule 3: 0.5 X 
0.6866 = 0.3433 inch. 

To find the addendum, use Rule 5: 0.5 X 0.3183 = 0.15915 inch. 

To find the pitch diameter of the worm, use Rule 7: 2.5 — 2 x 
0.15915 = 2.1817 inches. 

To find the bottom diameter of the worm, use Rule 8: 2.5 — 2 X 
0.3433 = 1.8134 inch. 

To find the gashing angle of the worm-wheel, use Rule 9: 2.18 X 
3.14 -f- 1 = 6.845 = cot. 8 degrees 20 minutes, about. 

To find the pitch diameter of the worm-wheel, use Rule 10: 45 X 
0.5 -¥- 3.1416 = 7.1620 inches. 

To find the throat diameter of the worm-wheel, use Rule 11: 
7.1620 -f 2 X 0.15915 == 7.4803 Inches. 

To find the radius of the throat of the worm-wheel, use Rule 12: 
(2.5 -*- 2) — (2 X 0.15915) = 0.9317 inch. 

The angle of face may be arbitrarily set at, say, 75 degrees. In this 
case. The "trimmed diameter" is scaled from an accurate drawing 
and proves to be 7.75 Inches. 

To find the distance between centers of the worm and wheel, use 
Rule 15: (2.1817 -4- 7.1620) -f- 2 = 4.6718 inches. 

To find the minimum length of threaded portion of the worm, use 



Rule 17: 7.4803 — 4 X 0.15915 = 6.8437 

V 7.4803' — 6.8437' = 3 Inches, approximately. 

It will be noted that the ends of the threads in Fig. 2 are trimmed 
at an angle instead of being cut square down, as in Fig. 1. This gives 
a more finished look to the worm. It is easily done by applying the 
sides of the thread tool to the blank Just before threading, or it may 
be done as a separate operation in preparing the blank, which will in 
either case have the appearance shown in Fig. 4. The small diameters 
at either end of the blank in Fig. 4 should, in any event, be turned 
exactly to the bottom diameter shown in Fig. 2, and obtained by 
Rule 8. This is of great assistance to the man who threads the worm. 

Jla<tMwry, Jt/» 

FllT' 4* Shape of Blank fbr Worm 

as he knows that the threads are sized properly as soon as he has 
cut down to this diameter with the end of his thread tool. This 
always supposes, of course, that the thread tool is accurately made. 

Formulas for the Design of Worm Oearing 

For the convenience of those who prefer to have their rules com- 
pressed into formulas, they are so arranged in the following. The 
reference letters used are as follows: 

y = number of teeth in worm-wheel. 

n = number of teeth or threads In worm. 
P" = circular pitch of wheel and linear pitch of worm. 

I =lead of worm. 
g = whole depth of worm tooth. 

t' = width of the thread tool at the end. 
8 = addendum or height of worm tooth above pitch line, 
o = outside diameter of the worm. 
d = pitch diameter of the worm. 

b = bottom or root diameter of the worm. 

p = helix angle of worm and gashing angle of wheel. 

d r= face-angle of worm-wheel. 
D = pitch diameter of the worm-wheel. 
O = throat diameter of the worm-wheel. 
0' = diameter of the worm-wheel to sharp comers. 
U = radius of curvature of the worm-wheel throat. 


= velocity ratio. 

= distance between centers. 

= threaded length ot worm. 
J = n X P' 
= 0.6866 P' 
r = 0.311^ 
8 = 0,3183 P' 
, o = d + 3s 
(1 = — 2« 
6^ff — to 


AD — I.IIM" 

Cotangent /J = 3.U16d-i- I 


= D+ 2s 

t7 = ^i0 — 28 

0' = 2 (U — r7coai/2) + 

R = 7f -i-n 



A model drawing of a worm-wheel and worm, properly dimensioned, 
is shown in Fig. 5. This drawing follows, in general, the model draw- 
ings shown by Mr. Burlingame in the August. 1906, issue of Machinebt, 
taken from the drafting-room practice of the Brown & Sharpe Mfg. 
Co. In cases where the worm-wheel is to be gashed on the milling 
machine before bobbing, the angle at which the cutter is set should 
also be given. This is the same as the angle of worm tooth found by 
Rule 9. In cases where the wheel is to be bobbed directly from the 
solid by a positively geared bobbing machine, this information is not 
needed. It might be added that it is impracticable with worm-wheels 
having less than 16 or 18 teeth to gash the wheel, and then hob it 
when running freely on centers, if the throat diameter has been deter- 
mined by Rule 11. 

When worms have a large helix angle (15 degrees or more), the di- 
mensions of the tooth should be measured at right angles to the helix. 
In such cases, the following changes should be made in the formulas 
Just given. 

Let P'n = normal circular pitch = P' cos /3. 

Formulas (3), (4), and (5), and the corresponding rules, should 
then be written as follows*. 

or = 0.6866 P'„ (3) 

r= 0.31 P'n (4) 

« = 0.3183 P'n (5) 

When these changes are made, all the other formulas will give correct 
results when used in their original form. 



If a worm and gear of standard proportions are brought into mesh, 
we have at the bottom of both the thread of the worm and teeth of 
the gear a clearance equal to one-tenth of the thickness of the thread 
or tooth at the pitch line. The clearance at the root of the gear tooth 
is obtained by enlarging the hob over the diameter of the worm, by 
an amount equal to two clearances, while the clearance of the tooth 
in the thread bottom is taken care of by the proper sizing of the 
gear blank. 

While it may be customary practice to make the hob an exact dupli- 
cate of the worm except in the one item of outside diameter, a hob 
proportioned as suggested in Fig. 7 is recommended as one that will 
give much more satisfactory results, and be found to be well worth any 
additional trouble in construction required beyond that for the style 
ordinarily used. The peculiar feature of this hob is that it is an 

* Machixxbt, September, 1007. 



exact opposite of the worm with respect to the proportions of the 
thread shape; the depth below the pitch line in one case being equal 
to the height above the pitch line in the other. The object of this 
is to have a hob that will form the complete outline of the tooth and 
make it absolutely certain that the standard proportions of tooth and 
clearance are obtained. Thus, should the diameter of the blank be 
large, the hob will trim off the top of the gear teeth to the proper 
length, when the proper center distance is maintained. 

There is another point that is generally overlooked, and that is the 
necessity for having the corners of the thread rounded over, and for 
providing a liberal fillet at the root of the thread. The radii of the 
rounded corner and the fillet may be as large as the clearance will 
allow, which would be one-twentieth of the circular pitch of the thread. 

The effect that this fillet and rounded thread have on the shape of 


Fl«. O. 

Dimension* of Worm 

the tooth is something that greatly increases the quality of the gear 
and the strength of each individual tooth. The rounded corner on 
the thread points does away with any tendency to scratch the surface 
of the tooth in the cutting action, and leaves a much larger fillet at 
the root, greatly increasing the strength. The fillet at the bottom of 
the thread rounds off the top of the tooth in the worm-gear, removing 
any burrs, and leaving a nicely finished product. This fillet also 
removes the dangerous tendency of the hob to develop cracks in the 
hardening process — a common source of trouble even where care is 
taken. Fig. 6 shows the proportions of the worm in comparison with 
the hob in Fig. 7. 

In forming the hob, much can be gained by making a special form 
tool of correct proportion that will leave no chance for error; the 
only dimension needing care then, is the diameter. Such a tool ia 
shown in Fig. 9. The figure is dimensioned by formulas, so that a 
tool for any pitch can be easily proportioned from it. This tool may 
be made by using a gear caliper without resorting to the protractor, 
or the protractor may be used in laying out the angle. This tool may 
be made without side clearance, providing that the sides incline in 
the same direction and at the same angle that the thread takes, but 
under ordinary circumstances, where only one hob is to be made, 
little is gained by having no side clearance. Clearance may be made 



(ml7 roughly approximated hy a comparatively email number of long 

The cutter used In gashing the hob sboald be about ^ inch thick 
at the periphery for hobs of ordinary pitch, while for those of coarser 
pitch a cutter 14 Inch thick would be much better. The width of the 
gash at the periphery of the hob should be about two-fltths the pitch 
of the flutes. The cutter should be sunk Into the blank so that it 
reaches from 3/16 to % Inch below the root of the thread. Fig. 8 
shows an end view of a hob gashed according to these rules. 

Where a hob is to be used to any great extent, and Is subject to 
much wear, It would be advisable to Increase the diameter above the 

dimensions given from D.OlO to 0.030 Inch according to its diameter 
and pitch, to allow for decrease in diameter due to the relief, and 
caused by grinding back the cutting face In sharpening. 

Hobs are generally fluted parallel with the axis, but It Is obvious 
that they should be gashed on a epiral at right angles with the thread 
helix In order that the cutting face may be presented with theoretical 
correctness; but the trouble encountered in relieving the teeth on the 
ordinary backing off attachment la the cause of the common mode 
of fluting. When the pitch or lead Is coarse In comparison with the 
pitch diameter of the hob, so that the angle is correspondingly steep, 
it may be best to flute on the normal helix, and If the hob cannot be 
machine relieved, it may be backed off by hand. 

The amount of relief depends much on the use for which the hob Is 
Intended. A hand hob tor hobbing a gear in position may be made 
with little or no relief, while hobs used on hobbing machines may have 
much more relief than those used on the milling machine. 




At the left of Fig. 10 is a sectional view showing a hob in the act 
of putting the last finishing touches on a worm-wheel. The hob is 
supposed to be a new one and is shown in the condition it is in when 
first received from the makers. At the right of Fig. 10 is shown the 
same hob putting the finishing touches on a worm-wheel similar to 
that in the first case. The hob in this case is represented as having 
been in use for a considerable time, and having been ground 
down to the last extremity, ready to be discarded for a new one. 
A study of this cut will show that if the hob is made in the first 
place to properly match the worm which is to drive the wheel, it 
w^Ill not, when worn, cut exactly the proper form of tooth in the blank 
to mesh with that worm. The teeth are cut to the same depth in 
each case, this being necessary in order to make a proper fit with 
the worm, which is the same in each case and is set at the same 
center distance. The grinding away of the worn hob has reduced its 
diameter by an amount indicated by dimension h. Us center is there- 
fore at P on the line A B, which is ofTset by a distance represented by 
dimension a from the line CD on which the center of the new hob 
is located. This reduction in diameter as the hob is ground away 
from time to time, so evidently follows from the construction of the 
relieved hob. that it scarcely needs to be explained. 

It is said of relieved hobs that they can be ground without changing 
their shape. This is true so far as the outline of the cutting edge is 
concerned, but it will be evident on examining the conditions shown 
at the right hand of Fig. 10, that whatever the outline of the cutting 
edges, a new hob of radius R will not cut exactly the same shape 
teeth in the blank as the worn hob with radius r. The elements of 
the tooth surface it generates are struck from a center P, removed 
by dimension a from center O' which is the location of the axis of 
the worm with which it meshes. 

It is possible, and perhaps practicable, to overcome this slight error; 
that is, to so design and use the hob that it will cut as correct teeth 
when worn as when new. In Fig. 11, dotted line A A represents the 
outlines of a new hob in the act of finishing the worm-wheel shown. 
Were a hob, ground as shown at the right of Fig. 10, to be substituted 
on the arbor for this new hob, without altering the adjustment of the 
machine except to move the hob endwise and bring it in contact with 
the teeth of the wheel on one side, this hob would be represented in 
Fig. 11 by the full line B B. It is evident that the left-hand cutting 
edges of this hob coincide (to the depth they extend into the wheel) 
with those of the new hob represented by outline A A. They will, 

* JiACMiinEUT, May, 1007. 


thsrefore, ao far w they extend, cut Identically similar and correct 
tooth curves with the new bob. 

Teeth cut with this worn bob would, however, evidently have tvro 
faults. The space would be too narrow at the pitch line by a distance 
measured by dimension m. and they would not be cut deep enougb 
In the blank by a distance measured by dimension n. Our problem 
Is to so alter the design and application of the hob. that, even when 
worn, we can cut the teeth deep enough and the space wide enough. 

Fig. 12 shows these conditions fulfilled. Dotted line C C shows the 
outline of the proposed hob when new. The only difference between 
the proposed hob and the regular one, whose outlines are shown by 
the dotted line 1 A In Fig. 11, Is that the teeth have been lengthened 
by an amount equal to dimension o. The bob Is fed In as was the 
case with the new hob In Fig. 11 until the distance between Its center 
line and that of the blank Is the same as tbat between the center line 
of the worm and the wheel in the finished machine. The Increase In 

radius, tben, by an amount o, makes the bob cut a clearance deeper 
than Is necessary by that amount. In a spur gear this would doubtless 
be a bad thing, since It would make the tooth slenderer and therefore 
weaker. A worm-gear, however, If designed to be sutOclently durable 
for continuous use, Is almost certain to be several times stronger than 
necessary, so that the slight weakening Involved in the change la not 
of great Importance. When the bob is warn to tbe shape shown by 
the full outline D D. the hob is evidently of the same diameter as 
the new one In Fig. 11, represented by dotted outline A A. Our tooth 
space, however, as before explained-, will be too narrow by the amount 
m In Fig. 11 or p in Fig. 12. To widen It out sufficiently, It is there- 
fore necessary for us, after the hob bas been fed in to the proper 
depth, to silU continue the cutting action, feeding the bob endwise, 
however, until It has been displaced to the position indicated by out- 
lines D' D'. The resulting tooth Is evidently identical wltb tbat given 
by the new hob A A In Fig. 11. 

It will be understood that when the hob In Fig. 12 Is new, it will 
not have to be shifted end-wise at alt, since It will cut a tooth space 
of the proper width as soon as fed to depth. It will, however, cut a 
apace deeper than necessary by an amount o. The worn hob, on the 
other hand, bas to be shifted longitudinally by an amount p and cut« 
to exactly the required depth. These represent the t 





Different authorities and writers on mechanical subjects have always 
held very different opinions regarding the location of the pitch circle 
of a worm gear. No better example of these differences in opinion 
can be given than by repeating a discussion in relation to this inter- 
esting subject which took place in the columns of Machineby, during 
1905. The subject was brought up by Mr. Oscar E. Perrigo, who, in 
describing the feed arrangement of a heavy turret lathe, into the 
design of which the worm a£d worm-gear entered, found occasion to 
state his opinions in regard to the construction of this mechanism. 
Mr. Perrigo says*: 

"Many good mechanics are so prone to object to any kind of a worm- 
gear, and can cite numerous examples wherein they have proven 
failures and utterly worthless for the purposes intended, that there is 
a very strong prejudice against them in any form. The writer is of 
the opinion that there is really only one practical objection to a 
properly constructed worm-gear, and that is, it must be constantly 
lubricated, and men running machines in which they are used are 
very liable to forget this fact altogether. The principal, and almost 
the only reason why worm-gears fail to give satisfactory results is 
that usually they are not properly designed at first. Another is that 
they are not properly hobbed out, and sometimes not hobbed at all. 
It is the purpose of this article to point out how they should be 
designed in order that they may be successful. 

"There are various methods for determining the diameter of the 
pitch circle of a worm-gear. One authority takes the outside diameter 
of the turned blank at its smallest diameter, or throat, as proper. 
Another takes the diameter of the bottom of the teeth at the extreme 
edge of the cut gear; stil) another, the point where the pitch line of 
the worm intersects the center line passing through the worm and 
worm-gear. All these are more or less in error, as they do not 
take proper account of the width of the face of the gear. If the teeth 
are straight, as in a spur gear, we naturally take a point in the center 
of the teeth (after subtracting the clearance) as the pitch line. Now 
when we have a curved tooth it obviously is not proper to do this, as 
the actual working pitch diameter must be somewhat larger than this; 
but how much larger should evidently be determined by the amount 
of contact with the worm, that is. the angle within which this contact 
is to be, the width of face being in turn controlled by the diameter 
of the worm. 

"Practically, the face of the worm gear is about equal to one-half 

* Machinbbt, .Tune, 1005. 


working deptb ot.the tootb. Where tbe working deptb. aa In standard 
practice, la equal to 0.6366 tlmee tbe linear pltcb, and when P" la tbe 
linear pitch, o tbe outside diameter, and d the iiltcb diameter ol tbe 
worm, this fact may be expreeaed by the following formula: 

(1 = — 0-6366 J" (1) 

In Fig. It we have a aectlon through a worm and worm-gear. The 
pitch circle for the worm, according to atandard practice, 1b located 
aa shown tangent to the line E, which la the pltcb line of tbe worm- 

Ptg. 14 Fig. 1» 

gear. On inspection of the figure It la aeen that while the addendum 
of the worm and worm-gear are equal at the center line A A. they are 
not at any other point along the pitch line, either to tbe right or the 
left, A section taken through tbe gear on tbe line A A would reveal 
teetb similar in shape to those of a spur gear of the same pitch and 
number of teeth. But how does this shape of tbe teeth vary as we 
shift this line either side of the central position? Let us show this by 
example, taking tbe case of a worm having a single thread of 1-Inch 
pitch. By taking a aectlon on line B B Instead of tlie center line A A 
we obtain Fig. 16. Tbla figure shows plainly that the faces of tbe 
teetb of the gear are considerably longer than the flanks. It Is easily 
Been that tbe greater tbe angle a la, the greater will this difference 
be, and vice vena, until we reach the central position, where there Is 


no dlKerence. Ttaerefore we see that this angle a plays an Important 
part In the design of a Bucceseful worm-gear. 

This angle Is not the only cause of distortion in the shape of the 
tooth. With a little tbought It will be seen that the angle of the helix 
also Is a cause lor further Irregularity. To Illustrate this we will take 

the case of a worm having the same pitch, but having three threads 
Instead of one. giving a lead of 3 inches. A section of this at BB is 
shown In Fig. IT. These conditions have the effect of prodnclng even 
longer faces than do those in the former case. 

What can he done to remedy this defect? We can shorten the faces, 
but when we do that at this point we do so all along the face of the 
gear and thug change the shape at A A, where It Is normal. There- 
fore, the best we can do is to divide the difference at the two extreme 
points — A A and B B. This can be done as follows: In an ordinary 
spur gear of standard proportions the pitch line is locat«d at a point 
midway of the working depth. From Fig. 15, which shows the end 

FIi. IT. BsctlDS Bl Lias BB. ng. 14, Triplt-lbnad Woi 

view of a worm, we see that the total working depth Is equal to W, so 
that from the foregoing statement the pitch line ehoutd pass through 
a point situated at a distance equal to one-halt of W from tbe outside 
of tbe worm, making d the pitch diameter of the worm. 
By an inspection of Fig. 15 we may derive the following formula: 

0.6366 P'l 

2 / 

cos — I 0.6366 P'l (Z) 

, we may obtain tb« value ot d la terms of o, f 

« /o V 

(I = — + C08— I 0.6366 P'l 

2 2 \2 / 

Solving this laet equation for o, we have the means for flndlng the 
outside diameter when d, P' and a. are given: 

2d + 1.2731^ COB — 

Formulas (3) and (4) may be used for obtaining tbe pitch diameter 
of any worm when the outside diameter la known, and vice verm. 
It Is quite evident, says Mr. Edgar, that the method given by Mr. 

Perrlgo for obtaining the pitch diameter of the gear la based on this 
''principle, but It la only an approximation, the variance between Its 
results and those of the formula increasing with the angle a. The 
dltFerecce for the example we have been investigating will be seen in 
Fig. 14 where O is the line as located by bis method, F that by the 
formula, and E the standard location. 

To show tbe difference this change in location of the pitch line 
makes In the tooth shape as compared with the usual practice, sections 
have been drawn at B B tor both a single- and a triple-threaded worm 
of 1-lnch pitch. Figs. 18 and 19. respectively, show these sections. 
Here we see that while the faces are yet conalderably longer than tbe 
flanks, the shape Is Improved. The difference between Fig. IS and a 
normal section Is very slight and hardly noticeable, and while the 
shape In Fig. 19 is somewhat freakish, It has all the properties of a 
smoothly running gear. 

But someone may ask what all this has to do with the durability 
of the gear. It is this: It has been proved that the friction of 
approach Is much more in amount than that of the release. This 
friction ot approach occurs between the face of the driven gear and 
the flank of the driver. Now If these particular elements of the tooth 
are extra long, the friction is proportionately increased over what ft 


would be In a normal tooth. The trlctlon ot motion Is always accom- 
panied bf wearing of tbe surfaces In contact; therefore In order to 
Increase the Ule of the gear, we must decrease tbe friction to a mini- 
mum. This we have done hy locating tbe pitch line In accordance 
with tbe formula. 

In order to Illustrate the extent to wbicfa some designers go to - 
eliminate tbe friction between the surfaces of the teetb In contact, 
tbe case of some special forms of clock gearing ma; be cited wberw 
tbe driver Is made with teetb bavlng no flanks and the driven gear 
with teetb having no faces, fixing all the contact at the period of 
release. The importance of this point is easily ascertained by observ- 
ing the wear on the teetb of a pair of gears that run constantly In 
one direction. 

Tbe tooth curves In the above figures were obtained by tbe tracing 
cloth method described In Unwln's "Machine Design." The subject in 

hand, however, does not require or warrant the descrlptioa ol this 
method here. . 

Finally, Mr. Ralph E. Flanders added to tbe discussion by a more 
fundamental study into the principles Involved tban had been under- 
taken by any of the previous writers. His analyzation of the subject 
clears some ot the doubtful points at issue. In order to give a com- 
prehensive Idea of bis statements, his treatment of the question has 
been given verbatim in the following*: ^ 

On tbe I<ocatlOD of the Pitch Circle Id Worm Gearing 

Mr. Perrlgo and Mr. Edgar, in their recent contributions on this 
subject, have called attention to some important points In connection 
with this form of gearing. The writer feels, however, that the recom- 
mendations they make cannot be followed blindly, but must be applied 
with a full knowledge of the limitations within which these recom- 
mendations are useful, it Is the purpose of the present article to 
point out these limitations. 

Mr. Perrlgo describes a worm and a worm-wheel which he has Incor- 
porated in the teed mechanism of a screw machine. Made in the way 
he describes, this worm and wheel have outlasted everything of their 
kind In his previous experience, and if the cases with which he men- 
tally compares this one have no other important points of difference. 

* HACHiratT, NoTCDiber. : 


hla confidence Is certalnlr JUBtlfled. Untortunatelr, tbis point iB not 
covared, and so we are left without a solid fouodatlon on which to 
twse our Judgment. 

The feed worm at a screw machine. If It Is of the clan in which 
the worm la dropped out of engsRement when the feed is released, 
does Its work under peculiarly trying clrcum stances. The writer's 
experience In screw machine design has led him to believe that the 
proper proportioning of these parts la a matter of considerable Impor- 
tance. Consider the case of a bronze wheel and a hardened steel worm 
working under the pressure of a heavy cut: When the worm la 
released from engagement with the wheel, under the pressure of this 
heavy cut. the sharp, hardened comer of the worm-tooth goes alldlns 
down the face of Its corresponding tooth In the wheel, giving It a last 
Jig as it Jumps bjr the corner. The necessity for quick handling 


demands that the momentum of the revolving parts of the feed 
mechanism be kept as lo\^as possible, so the peripheral speed of the 
worm-wheel must be as low as possible In comparison with the rate of 
movement of the slide. This. In turn, requires the worm to work 
under heavy pressure. It Is not practlcatfle to locate the feed releass 
between the worm and the clutch, especially If the feed Is to be 
stopped automatically, because It Is difficult (o handle a toothed clinch 
under a severe torsional strain. Usually this problem Is settled by a 
compromise whose success depends on the Judgment of the designer; 
the peripheral speed ot the worm-wheel Is made as high, and conse- 
quently, the worm thrust is made as low aa is possible without too 
great a sacrifice In rapidity of handling. In large machines this diffi- 
culty may be overcome by connecting the pinion shaft to the worm- 
wheel by frlctlonal contact, accomplished by tightening up a supple- 
mentary pilot mounted In front of the main pilot wheel; the auto- 
matic release is effected by stopping the rotation of the worm. 
Another point that militates against the durability of this mechan- 


ism when a releasing worm is used, is the indeterminate location of 
the worm. While it is obvious that a worm cannot be adjusted in a 
direction parallel to the axis of the worm-wheel, it is not generally 
realized that the center distance between its axis and that of the 
wheel cannot be varied without losing the perfect action which exists 
when the worm is properly located. That this is so will be evident 
from Fig. 20. In this cut T^ and T are sections of a worm tooth 
taken on lines 1-1 and 2-2 respectively,. The section on 1-1 is evi- 
dently that of an involute rack tooth and so possesses the character- 
istic property of correct action at any center distance, so long as 
its straight face is in contact with the mating gear tooth. As we leave 
this section, however, and approach section 2-2, the tooth outline 
gradually loses its resemblance to the involute form and takes a 
shape in which positive location is absolutely necessary for correct 
action, as is shown by the curved sides. This variation from the 


jHVMlMl^f ^* mm 

Flff. 81 

involute shape is especially nutrked In worms of large helix angle 
and consequent high efficiency. 

Now, if the worm is slightly separated from its correct location in 
the mating wheel and no sideways motion is allowed, it will be seen 
by observing the relative angularity of the outlines of the faces in 
the curves T and T, that the contact will at once lose its character 
of line contact, extending across the full width of the gear, and will 
be concentrated in point contact on the extreme outer edge, where 
correct action is impossible except at the calculated center distance. 
For working under heavy pressure, then, it is necessary that the worm 
agree in shape with the hob which cut its mate, and that its axis 
exactly coincide with that of the hob when this was taking its finish- 
ing cut. These requirements may be met easily in high-grade work, 
such as is the rule in making a worm-gear drive for a gear-cutter 
spindle or an elevator, but such workmanship is very far from the 
haphazard fitting that a releasing feed worm must necessarily get. 

It has occurred to the writer that the worm, or worms, in Mr. Perri- 
go's turret lathe, must be of considerably greater helix angle than is 
usual in feed gearing. The unusual arrangement of a double reduc- 



lion is employed, making use of two sets of worms and wheels in 
series. Unless the feed shaft rotates at high speed, or the feed is 
exceedingly fine, this must mean that the reduction in each set of 
gears is small, which in turn predicates a large helix angle and an 
efficient gear. Mr. Perrigo must, then, give us more definite informa- 
tion if his experience is to be valuable as a permanent record in the 
matter of the location of the pitch line. Was his machine furnished 
with a releasing worm for a feed stop, and were the machines with 
which he compares it so equipped? How carefully was the worm 

Line of Action 



Mmthtiwf. Jf. K 

Flff. 22 

fitted in the last machine and in the former machines? What are 
the helix angles of these worms and former unsuccessful cases? What 
materials were used in the different sets of gears which are under 

Mr. Edgar has shown quite plainly that the advantage to be gained 
by lessening the diameter of the pitch circle on the worm is due to 
the fact that in such a case the contact between worm and wheel takes 
place for the most part after the teeth have begun to recede from 
each other. In Fig. 22 the worm, with its pitch line at OH, driving 
the wheel in the direction shown, will always make contact with it 
along the line of action. C D. The pitch line is located, as usual, half- 



marked, serves no useful purpose. This area of the worm tooth ex- 
tending above the interference line, is seen to be slight for a thirty- 
tooth wheel of standard design. An inspection of the cut will show 
that there are always two and sometimes three teeth in contact The 
contact takes place about equally each side of the center line, inclin- 
ing toward the favorable side, since line FD^ on the release, is some- 
what longer than OF, on the approach. 

In Fig. 23, we may see what effect has been produced by increasing 
the addendum of the worm, as we are advised to do. In the first place. 


Line of Action 

Flff. 28 


4fti«k^Mf^ jr.; 

the interference line, through point D, is lowered so far that the use- 
ful area of the teeth has been greatly decreased. There is no work- 
ing contact on the wheel teeth inside of the base circle, nor do the 
worm teeth serve any useful purpose above the interference line. 

The strength of the wheel tooth has been decreased. The great 
length of useless worm tooth extending above the interference line 
has cut a deeper clearance into the flank of the wheel tooth, thus 
weakening it at the very point where it needs strength. On pages 68. 
69. and 71, of the Brown ft Sharpe "Treatise on Gears," will be found 
three illustrations which show this point very clearly. One case is 
that of a twelve-tooth worm-wheel of standard design, which gives a 


badly undercut flank. In the next illustration the worm-wheel has 
been bobbed according to Mr. Edgar*s rule, and* the result is worse 
than in the first case. The last illustration shows the pitch line 
thrown clear to the outside diameter of the worm, this being advised 
as the proper remedy to secure a tooth of sufficient strength and bear- 
ing surface. 

Referring again to Fig. 23, the number of teeth in contact has been 
reduced until there is only one constantly in use, though two are in 
position to work most of the time. The single gain to be derived in 
return for the advantages that have been lost lies in the fact that a 
greater percentage of the line of action lies on the releasing side of 
pitch point F than before, since FD is noticeably longer than FC. 

Of course only the action on the center line has been analyzed. The 
writer has studied the action at sections made in different places in 
the worm-wheel face, and it looks as though the conditions at the 
center line were a fairly good index of what is going on nearer the 
sides. The line of contact appears to rise slightly toward the outside 
of the worm as it leaves the center (going toward the leading side of 
the worm), and then drops again toward the edge of the wheel. On 
the retreating side of the worm the contact drops continuously. This 
tends to minimize the effect that the width of the wheel has on the 

How, then, should the pitch line be located? It seems to the writer 
that the problem is so involved that in a case of any importance the 
designer should not trust to any empirical rule, but should plan each 
case with reference to these four points: area of bearing surface in 
the teeth, strength of the teeth, number of teeth in contact, and loca- 
tion of contact, whether in the approach or the release. To these 
should be added a fifth point, more important than any of the others, 
as far as efficiency is concerned, and that is in relation to the helix 
angle of the worm: it should be as large as possible. 

Taking all these points Into consideration, it would seem that, for 
worms and wheels made as they usually are for ordinary service, from 
ordinary materials, and with ordinary carefulness of workmanship in 
making and fitting, It is hardly worth while to bother about changing 
the location of the pitch line for the sake of having the contact on 
the release. It introduces too many other complications into the prob- 
lem. Still, if there Is any one who wants to try the effect of altering 
the worm and wheel dimensions with this end in view, here are a few 
suggestions in the shape of formulas to add to those of the two con- 
tributors who have previously written on this subject. 

Let ^ = number of teeth In wheel. 
P' = linear pitch of worm. 
= throat diameter of wheel. 
= outside diameter of worm. 
D = pitch diameter of wheel. 
d = pitch diameter of worm. 
(/ =z= pressure anglo^ 


= := center distance between the worm and the wheel. 


S' = effective height of worm tooth above pitch line (see Fig. 23). 
An Inspection of Fig. 23 will show that 8' may be expressed as follows: 

D sin* a 

fif' = 


If we limit the height of our tooth to this line, thus allowing no 
Interference, we may use the following formulas, It being considered 
that we have given (7, P' and N. 

D = (5) 

d = 2(7 — D (6) 

o = d + l>sln«o (7) 

= D + 1.273 P' — Dsln«o (8) 

For a pressure angle of 14^ degrees and an allowed Interference 
equal to that of a standard worm In mesh with a 25-tooth wheel, these 
last two formulas will become: 


o = d-f— (9) 


= 0.923 D + 1.273 P' (10) 

These formulas will give as much of the contact on the release as 
Is possible without too much undercutting; the location of the pitch 
line will, of course, vary widely. Formulas (7) and (8) (when a = 
14% degrees) are good for any number up to 64 teeth, and Formulas ^ 
(9) and (10) up to 52 teeth. Above these numbers the formulas 
would bring the pitch line below the root diameter of the worm, which 
Is needless; so for such cases, Formulas (7), (8), (9), and (10) should 
be replaced by the following, which will keep the pitch line within the 
working area of the tooth: 

o = d + 1.273 P' (11) 

= D (12) 

All that has been said In the preceding paragraphs refers only to 
worms whose tooth outlines show straight sides on an axial section. 
If, as Is often the case with steep-pitched worms, the cutting tool is . 
made with straight sides, but tipped up at an angle to agree with the 
helical angle of the worm, an axial section will show teeth with curved 
sides whose shape will depend upon the helical angle. In such a case 
as this it is impossible to apply any of the rules which govern the 
action of Involute teeth, and the only way to go about the matter of 
locating the pitch line to suit the Ideas of the designer is to make a 
careful analysis of the tooth action on various sections. This opera- 
tion would be so troublesome and tiresome as to be impracticable 
under any ordinary circumstances. 



The HIndley type of worm-gear was flrat used In Hlndley's divid- 
ing engloe.t and was, by the laventor, considered superiOT to the ordi- 
nary type, in wearing quality. Investigation has prscticallj settled 
that the nature of contact between the worm thread and tbe teeth of 
the ordinary worm-wheel is that of line conta(:t, extending across the 
tooth on the pitch line. It has also been fairly well proved In prac- 

tical exaroplee that the contact is of a broader nature on account of 
the elasticity of the materials used In the construction. The convex 
aarfaces of contact are flattened consldevably under pressure and thus 
for practical purposes make actual surface contact. The contact in the 
ordinary worm and worm-wheel type Is limited to two teeth of the 
wheel and worm thread, at most. 

Comparison of Ordinary and HIndley Worm OearlDff 

The conditions are much different In the case of the HIndley worm, 

and It la the Intention in this chapter to ehow wherein the difference 

lies. As this style of gearing is uncommon to most of us, a few words 

•Micni!(i.«*, December. 1808. 

tThe lllndtey senr. bb uKd In tbe HlmHe; dlTldlTiK engine, li descHtked by 
Hmraton. bIbo Lj WIIIIi iPrlnclpIci of MecttanUiD. 1891). Various modlBcitloni 
at the Fllndlcy gtti, IncIadlDi Jniwn') wlncb. are llloBtrated In Bealeaax'i "C«n- 
■trnctor." piK« 14:1. 


regarding its construction will not be out of place. Fig. 24 illustrates 
the Hindley worm, showing the theoretical form. This worm is 
not of cylindrical shape, but is formed somewhat like an hour-glass, 
after which it is sometimes named. The worm blank, being made 
smaller in diameter in the middle than at either end, conforms to the 
circumference of the wheel with which it meshes. The worm thread 
is cut by a tool which moves in a circular path about a center 
identical with the axis of the wheel with which it is to mesh, and in 
the plane in which the axis of the worm lies. The process is similar 
to ordinary thread cutting in the engine lathe, except for the differ- 
ence in the path of the tool, the tool having a circular instead of a 
straight path. 

It is evident that the worm shape is dependent on the particular 
wheel with which it is to run, and Hindley worms are not interchange- 
able with any other but an exact duplicate. That is, a worm cut for a 
Hindley gear of 50 teeth cannot be used successfully with a wheel of 
70 teeth, although the pitch of the teeth is exactly the same. In the 
ordinary type of worm gearing, one worm may be made to run with 
any number of diameters of wheels of the same pitch, and bobbed with 
the same hob. 

In action the two styles of worm-gear differ greatly, and both diverge 
widely in action from the case of a plain nut and screw, which may 
be taken to represent a worm and worm-gear, the latter of infinite 
diameter and with an angle of embrace of 360 degrees. In studying 
the action between the thread and teeth of the ordinary type of worm- 
gear, we must understand odontics, rolling contacts and the theory 
of tooth gearing, in general, in order to understand the action of the 
ordinary worm-gear. But, in studying the action of the Hindley type, 
we are concerned with no such theories, as the action is purely sliding 
and devoid of rolling contact. In the ordinary worm we have an 
axial pitch which is constant from top to root of the thread, while in 
the Hindley worm we have a section in which the pitch of the thread 
varies from top to bottom. 

The interference in the ordinary type of worm-gear is absent from 
the Hindley type, and the consequent undercutting and weakening of 
the teeth, therefore, is a feature with which the designer of the Hind- 
ley worm gearing does not have to contend. For this reason we are 
not limited in the length of teeth, by interference, as in the ordinary 
case. This fact permits a wide latitude in the choice of tooth shapes 
and proportions. In most examples we will find that the depth of 
thread is much greater in proportion to the thickness than in the 
ordinary worm-gear, in which the height is limited by reason of the 
interference at the top and root of the teeth. 

Nature of Contact of Hindley Worm Gearing 

The general idea of the Hindley worm gearing Is that there is sur- 
face contact between the worm and gear, and that the contact is gen- 
erally over the whole number of teeth in mesh. If such were the 
actual conditions, the Hindley type would surely be an ideal mech- 


anlsm for high velocity ratios, but that such Is not the fact Is the 
purpose of this treatise to polDt out. That the contact la of a superior 
nature we will not deny, nor that It Is much nearer a surface contact 
than exists In the ordlnarr worm sear. Ab a means of comparison, 
Figs. 25 and 28 are shown. Fig. 25 shows an axial section taken 
through the worm end gear of the ordinary type, while Fig. 26 shows 
a similar section through the Hlndley worm and gear. The "airy" 

appearance of Fig. 25 as compared with Fig. 26. Indicates a vast dllfer- 
ence In the nature of contact, and gives the advantage to the Hlndley 
type, wherein is the origin of certain false Ideas In favor of the latter. 
These Illustrations also show peculiar dltFerences In the action of the 
two types. The absence of rolling action In E^g. 26 is the most promi- 
nent, and it shows the similarity between this type of gear and a 
screw and nut. 

From an inspection of Fig. 26 we may feel sure that the contact on 

the axial plane is as shown, but as to the nature of contact in a plane 
either side of the middle plane we are In the dark so far as the draw- 
ing illustrates. Mr. George P. Grant has this to say concerning the 
contact of the Hlndley worm and gear: "It Is commonly but errone- 
ously stated that the worm (Hlndley) file and Alls lis gear on the 
axial section, ... It has even been stated that the contact Is be- 
tween Burtaces, the worm filling the whole gear tooth. ... It Is 


also certain that it (the contact) is on the normal and not on the axial 
section, and that the Hindley hob will not cut a tooth that will fill 
any section of it. The contact may be linear on some line of no great 
length, but it is probably a point contact on the normal, section." 

It is not clear what reason Mr. Grant had for saying that the con- 
tact is normal instead of axial; but there is every reason to believe 
that the contact is on the axial section since it is on this section that 
the teeth of the hob have a common pitch. The teeth have not a 
common pitch on any section at an angle with the axial section. For 
what reason would one expect to find contact on the normal section 
in this case any more than in the case of the ordinary worm? Since 
both styles of worm-wheels are bobbed with a revolving hob which 
lies in a plane perpendicular to the axis of the worm-wheel, the con- 
tact could hardly be on a normal section. 

Prof. MacCord states that he considers the contact to be line con- 
tact on the axial section, and he gives directions for obtaining the 
exact nature of the contact and also the thread and tooth sections. 
These directions, on account of the complicated nature of the method, 



Pl«. 27. DeTelopment of Ordinary Worm and Hindley Worm 

Spirals on a Plane 

are hard to follow. Much, however, can be found out by simple 
methods. In what follows, describing these simpler methods, the re- 
sults, of course, are of an approximate order, but they nevertheless 
give a means of comparison and a material basis for the line of argu- 

The Ideal Case Considered 

It is assumed that we are examining an ideal Hindley gear in which 
the worm and wheel are theoretically correct in shape and that the 
surfaces are perfectly smooth and inelastic. FYom the nature of the 
worm, the helix angle varies from mid-section to the ends, decreasing 
as the thread approaches the ends of the worm. The thread is spiral 
as well as helical. This change in the thread angle is caused by the 
increase in diameter at the ends of the worm and by the fact that 
the axial pitch of the thread decreases as it reaches the ends. The 
decrease in axial pitch is due, of course, to the circular path of the 
threading tool. If we take a development on a flat surface of a line 
scribed in the spiral path on the worm blank, as shown in Fig. 27, 
the change in the angle becomes noticeable. 

In the operation of forming the teeth of the gear, the blank is 
rotated, each portion of the hob working the tooth into shape so that 
it will pass the corresponding portion of the worm thread without 
interference, permitting a smooth transmission of motion. If each 


that It will do BO without Interference. It Is evident that the radtal 
section of the Bear at k must be the same aa at j. Since the worm is 
largest In diameter at fe, the curvature of the tooth on the radial sec- 
tion is dependent on the thresd at that point The curvature of the 
tooth at It: evidently Is that of an ellipse whose major axis Is A A,. 
Now, since the thread is made with angular sid»a, the hob could 
hardly act on the teeth of the gear the same at all points from k to ^ 
except on the axial plane where the relative shape of the hob thread 
Is the same for any position along the line of action (see Fig. 26). 
This Is evident from Fig. 30 at E, which point only touches at the 
mld-eectlon of the worm. Therefore we still have the line contact from 
top to bottom of teeth on the axial plane, but the construction. Fig. 

30. shows that the surface contact s. i, s, s. Figs. 2S and 29, doee not 
actually exist, but that the surface contact at the ends of the worm 
remaluB undisturbed. 

From the above we ma; safely conclude that the bob at j has but 
little effect on the actual shape of the tooth, and that its Influence 
Increases until k Is reached. Fig. 30 also shows a good reason why 
the contact may be considered axial Instead of normal, by the mere 
fact of the dllterences In curvature of worm and wheel at any point 
other than k. In practice the contact may appear to be surtace con- 
tact, but this, no doubt, is due to the Influence of the lubricating oil 
and the fact that materials of construction are distorted to some extent 
in form when subjected to pressure. This distortion permits the worm 
thread to Imbed itaelf into the worm-wheel teeth, somewhat broaden- 
ing the contact for the time being. The conditions as stated In the 
above discussion would be met In the case of a hardened worm and 
gear with surfaces finished by lapping. In practice the worm and 
gear are ground together, sand and water being used as the abrasive. 
This grinding wears down the roughness of the surfaces and tends to 
correct Irregularftles in form that develop In the bobbing process. 


Conclusions Beflrardinflr the Hindley Worm and Qear 

The following are the author's conclusions, derived from the investi- 
gation regarding the Hindley type of gear: 

1. The contact is purely sliding contact. 

2. The nature of the contact is linear, closely resembling surface 

3. Linear contact extends from the top to the root of the tooth. 

4. The contact is on the axial section. 

5. The thread section fills the tooth space on the axial section only. 

6. The mid-portion of the hob has little or no effect in shaping the 
teeth of the gear. 

7. Surface contact exists on opposite sides of the axial plane at the 
end of the worm thread and is intermittent in nature, because the 
end of the thread passes out of contact with the tooth in the revolv- 
ing of the worm. This contact is on a plane normal with the thread 

In practice it is usual to allow considerable back-lash between the 
thread .and che tooth of the worm and gear. This play tends to coun- 
teract bad workmanship, either in construction or erection. 



Bary to assume a value for /, which, if the condltton of determining 
the use ol the worm-gear is Its selMochlng property, should be assumed 
conservatively low. Unwln states under the authority of Prot. Brlggs, 
that a welt-fltted worm-gear will exhibit a lower coefficient of friction 
than any other kind of running machinery. Prof. Jones gives a 
series of values for the coefficient of friction of Bcrew gears, one of 
which la a pinion of 4 inches pitch diameter, the average value being 
/^0.06, corresponding to a rubbing velocity of 250 feet per minute. 
Mr, Haleey assumes /=:0.06, and Mr. Wilfred Lewis aays that when 
the worm-gear Is worked up to the limit ot its safe strength, a rub- 
bing velocity greater than 200 to 300 feet per minute will prove bad 
practice. It Is In heavy machinery where worm-gears are mostly used 
as self-locking transmission elements, and here they are usually worked 
up to the sate strength of the wheel; hence It is fair to assume /=:0,0K 

when designing a selMocklng worm-gear, and to limit the rubbing 
velocity to 200 feet per minute, and we have for the limiting value ot 
p at which the eystem will be self-locking: 

p = 0.05 IT d = 0.157 <J (2) 

The sliding velocity in feet per minute at the pitch line Is expressed by 

V = = 0.262(in (3) 

where d^the pilch diameter of the worm, and n^the number of 
revolutions per minute of the worm. 

Under the above asHumptlon, that tor continuous service and heavy 
pressures the sliding velocity should not be more than 200 feet per 
minute, we have as the limiting value ot d to avoid all cutting: 
0.2e2 n 
The exact nature of the surface of contact between a worm and wheel 
Is Involved In doubt; many claim It Is only a point; it certainly Is 
not large, and consequently a wide face for the wheel Is not needed 



If the angle a^ is made 60 degrees. It will make the face right for any 
ordinary worm of 4 to 6 inches diameter. 

There is in all worm gearing a very heavy end thrust on the worm- 
shaft, and also an outward force normal to the worm-axis, each of 
which must be suitably provided for in the design of the shaft and 
bearings. The end thrust may be taken by bronze washers slipped into 
the bearings at the end of the shaft, which may be removed when 
worn and replaced with new ones. Shoulders may be provided on the 
shaft, between which and the bearings bronze collars may be placed, 
these being split to enable new ones to be easily and quickly placed in 
position when the old ones become worn. Roller thrust bearings are 
very often applied to worms, and these as well as the bronze washers 
may be supplied with adjusting setHscrews to take up the wear, instead 
of renewing the washers. 

In Fig. 33 let P = the tangential force at the pitch line of the worm, 
d = the pitch diameter of the worm. Q = the tangential force at the 

Fl«. 84 

pitch line of the worm-wheel, E = the end thrust of the worm-shaft. 
F = the force on the worm-shaft normal to the worm-axis; then, fric- 
tion being neglected, 

Q = (4) 

In Fig. 34 let the force Q be represented by the line A C normal to the 
tooth side of the worm at the pitch line; draw AB normal to the 
axis of the worm, and B C parallel to the axis or coincident with the 
pitch line of the worm; then, when measured to the same scale to 
which AC was drawn, AB^F, and BC=3E. As the angle CAB Is 
75 deg. (for the 15 deg. Involute system) we have, 


— = sin 15 deg., and F = 0.259 Q (5) 


— = cos 15 deg., and E=: 0.966 Q (6) 

Taking friction into consideration, the force P,. tangential to the pitch 


line of the worm, which it is necessary to employ in order to produce 
a force Q tangential to the pitch line of the wheel, is given by Weis- 
bach as 

p»=g (7) 

in which 


The efficiency of the worm and wheel is then, 


— =e (S) 


Example: A single thread worm of 1-inch pitch, running 80 revolu- 
tions per minute, is to transmit to a worm-wheel a tangential force 
Q = 5,000 pounds, and is to be self-locking. 

From (3) 


d< , 

0.262 X 80 

or d may be as large as 9.5 inches before abrasion need be feared. 

From (2) 

p < 0.157 d; assume p = 0.125 d, 

then, as p = 1 inch, d = 8 inches, or the worm will require to be 
8 inches pitch diameter in order that the angularity of the thread 
may be small enough to make the system self-locking. It will be seen 
that the required diameter will be increased as the value of / is 
decreased, and in case the required diameter of the worm proves too 
great for practice, and the pitch cannot be reduced on account of con- 
siderations of strength, some outside aid, such as a brake or friction 
disk applied to the worm-shaft, will have to be adopted. 
From (7) 

P 1 

as h=: = = 0.04, we have 

nd 3.14 X 8 

0.04 -f 0.05 

P, = 5,000 = 451 pounds. 

1— (0.04 X 0.05) 
From (4) 

3.14 X 8 X P 

5,000 = , or P = 199 pounds. 

From (8) 

P 199 

— = = 44 per cent for the efficiency of the worm-gear. 

P, 451 

The formulas may, by starting with those for the efficiency, be used 
to determine the pitch diameter which will give the proper thread 
angle for any given pitch and degree of efficiency. 

It is clear from the foregoing, that a worm-gear of large pitch will 
require a pitch diameter of the worm altogether too large for practice, 
if it is to be self-locking, and that the system as usually designed may 
be expected to run backwards. To prevent this, a friction disk may 



be placed in the bearing which receives the thrust of the worm-shaft 
when the system is running backwards, and the diameter of the disk 
so proportioned as to Just hold the worm-shaft stationary under the 
impulse of the worm-wheel. 

The foregoing discussion neglects the effect of the thrust of the 
worm-shaft in its bearings, the frictional resistance of which must 
be added to that of the teeth to obtain the actual conditions of a 
self-locking system. This frictional resistance depends upon the values 
of the end thrust E and the normal force F already found, and the 
diameter and form of the bearing. In nearly all cases of worm gear- 
ing the mounting of the worm upon the shaft will be covered by one 

Fl«. so Ftff. 80 

of three cases, either unsymmetrically between the bearings, sym- 
metrically between the bearings, or over-hung. 
In Case 1, Fig. 35, the bending moment upon the worm shaft is, 

Fah 0.259 Qa& 

Af = = (9) 

L L 

In Case 2. same as Case 1. except that the worm is central between 

the bearings, and 

a = 6 = — 

the bending moment upon the worm-shaft is. 

0.259 Q L 

M = 

= 0.0647 Q L 


In Case 3, Fig. 36, the bending moment upon the worm-shaft is. 

lf = FL = 0.259gL (11) 

In each of the above cases the shaft is subjected to a combined twist- 
ing and bending strain, the twisting moment being the same in each 
case, T = PR, which is, however, so small as to be negligible in what 

In the following table the first column shows the several styles of 
Journals most commonly used for worm-shafts, the second column gives 
the moment of friction for each under a load in the direction of the 
arrow, the third column gives the coefficient of friction assumed, and 
the fourth column gives the tangential force P, at the pitch line of the 
worm, resulting from the resistance of friction in the Journals, and 
found by dividing the moment of friction in Column 2 by the pitch 
radius of the worm. 

There are always acting upon the worm-shaft the two forces F and 



E\ consequently to get the resultant retarding force tangential to the 
pitch line of the worm, we must take the sum of the resultants due to 
the frictional resistance of each force separately. Referring to the 
table, we will, for each worm-shaft, find the conditions shown at A, 
in addition to the conditions shown either at B, (7 or D, as the case 
may be, and the total resultant force P, at the worm pitch line will 
be the sum of the quantities given in Column 4 opposite the particular 

These frictional resistances developed by the journals act in a direc- 
tion helpful to the self-locking property of the worm, and enable the 
designer to use a larger thread angle for a given diameter of worm. 



style of Journal. 



Moment of 




i r sin. y 

8 (ri» — r«) 



Moment of Friction 



.04 Pd 









p r sin. 


.2 P (n» - 


Ti* — r' 

or a smaller diameter of worm for a given thread angle, thus keeping 
within the limits of good practice, and increasing the efficiency of the 
system for the forward movement. 

Having determined the force P, tangential to the worm pitch line, 
resulting from the frictional moment at the Journals, the angle of 
repose for this force acting with the force Q, as shown in Fig. 37, is 
given by the equation. 


tan x-=. — . 
The thread angle found previous to the consideration of the effect 

of the Journal friction may now be increased by the angle rr, making 
the thread angle a-\- x. This may be accomplished either by Increas- 
ing the thread angle, increasing the pitch, or decreasing the pitch 
Consider, now, that in the foregoing example, the worm-shaft is of 



the form In Case 2, the worm being central between the bearings, and 

the distance between bearings being 36 inches. 

Then, from (5) we have, 

F = 0.259 X 5,000 = 1,295 pounds, 
and from (6) 

E = 0.966 X 5,000 = 4,830 pounds. 
From (10) 

0.259 X 5,000 X 36 

M ^ = 11,655 inch-pounds. 


Assuming « = 10,000 pounds per square inch for the allowable fiber 
stress in the worm-shaft, we have 


M = — d,'« or d, = 2.28 inches. 

From the table, Case A, 

0.04 X 199 X 2.28 
P, = =18.15 pounds. 

FUr. 87 

From the table. Case B, 

0.1 X 199 X 2.28 

Jmduttrfmt.fttm, A.F. 


From (1) 

Pi = 

= 45.37 pounds. 

P, = 18.15 -f 45.37 = 63.52 pounds. 


tan X = = 0.0127 


x = deg. 44 min. 


tan a=: 

= 0.04 

3.14 X 8 
a = 2 deg. 17 min. 

a 4- ^ = 3 deg. 1 min. 
tan 3 deg. 1 min. = 0.053 


= 0.053 = ?^. and d = 6 inches, approx. 

If, now, we substitute these new values of h and d in equations (7) 
and (4), we continue as follows: 



Prom (7) 

From (4) 

From (8) 

0.053 4- 0.05 

Pj = 5,000 = 516 pounds. 

1— (0.053 X0.05) 

P X 3.14 X 6 
5,000 = , or P = 265 pounds. 


•= 51 per cent efficiency for the worm-gear. 

P» 516 

The total efficiency of the system, taking account of the journal fric- 
tion, will be 

P 265 

= = 46 per cent. 

P, + Pa 516 + 63.52 

It thus becomes clear that while the efficiency of the worm threads 
and wheel teeth has been increased above 50 per cent, the efficiency 
of the whole system, including the Journals, is below 50 per cent, and 
the system retains its self-locking property. It is evident that when 
running forward, the end thrust E upon the worm-shaft will be upon 
the opposite end from that when running backward, and on this ac- 
count a system may be designed to have a high efficiency on the for- 
ward movement and still preserve its self-locking property. 

If both the journals have roller bearings, and the end taking the 
thrust on the forward movement has a ball bearing, while the oppo- 
site end be made like Case C or D in the table, properly proportioned, 
the worm may be designed to show a very high efflxiiency on the for- 
ward movement, while the frictional resistance of the step bearing 
on the opposite end will cause the system to be self-locking by reason 
of the energy absorbed at the step bearing. 

The formulas may be put into more convenient form for this pur- 
pose, as follows: 

The designer will have, to start with, a knowledge of the force Q 
required at the worm-wheel, the force Pj at the pitch line of the worm, 
developed from the source of power, the pitch required for the worm- 
wheel, and the efficiency e for which he wishes to design the system. 

We then have, 


— = e, and P = Pie. 

Substituting this value for P in equation (4) and solving for d, we 


d = 

3.14 P^ e 
for the worm, neglecting the journals, when the journals and thrust 
bearings are roller and ball bearings, respectively, and 


(f = 

3.14 iP^ — P,) e 

when the journals and thrust bearings are considered. 



The m-orm being thus designed for the given eflkriencr on the forward 
movement, it remains to determine such proportions of the step bear- 
ing for the backward movement as will present enough frictional 
resistance to render the system self-locking. Let ej = the efficiency 
when the Journals and thrust are considered, then 

= Ci or P = c, (Px -I- P.) 

Pt + P. 

and substituting the value of P found above 

eP» = e,P,-i-e,P, 


Pt = 

Pi (e — e,) 


By equating this force P, to the proper quantity from Column 4 in 
the table of Journal resistances, the proportions required of the Journal 
or step bearing may be determined. 

Theoretical Bfflciency of Worm Gearing 

The following table gives the theoretical efficiency of worm gearing 
for a number of different coefficients of friction. Practical experiments 
carried out by the Oerlikon Company, Oerlikon by Zurich. Switzer- 
land, agree closely with the results from theoretical calculations given 
in the table. These experiments indicate that the efficiency increases 




AHOLs or Ikcldiatiox. 


10 dag. 

16 dag 


25d«g. |80deg. jasdeg 














































88 1 



















70 7 

77 8 



85 6 



86 9 



67 8 


79 6 

82 2 



85 2 













46 8 





80 3 




with the angle of inclination, up to a certain point. They also show 
that for larger angles of inclination than 25 degrees to 30 degrees the 
efficiency increases very little, especially If the coefficient of friction 
is small, and this fact is of importance in practice, because, for rea- 
sons of gear ratio and conditions of a constructive nature, an angle 
greater than 30 degrees cannot be employed. The coefficient of fric- 
tion increases with the load and diminishes to a certain extent with 
increase of speed. Besides the friction between the worm and the 
wheel teeth, there is also the friction of the spindle bearings and the 
ball bearings for taking the axial thrust. To obtain the best results. 


there must be trery careful choice of dimensions of , teeth, of the stress 
between them, and the angle of inclination. To show what can be 
done, the following are the results of a test with an Oerlikon worm- 
gear for a colliery winding engine: The motor gave 30 brake horse- 
power to 40 brake horse-power at 780 revolutions. The normal load 
was 25 brake horse-power, but at starting it could develop 40 brake horse- 
power. The worm-gear ratio was 13.6 to 1, the helicoidal bronze wheel 
having 68 teeth on a pitch circle of 7.283 inches, and the worm 5 
threads. The power required at no load for the whole mechanism was 
520 watts, corresponding to 2.8 per cent of the normal. The efficiency 
at one-third normal load gave 90 per cent, at full load 94%^ and at 
50 per cent overload 93 per cent. The efficiency of the toorm and wheel 
alone is higher, and knowing the no-load power, is calculated to be 
97% per cent. According to the table given, of theoretical efficiencies, 
this gives- the coefficient of friction as 0.01. To obtain a reduction 
of 13.6 to 1 with spur gears would have necessitated two pinions and 
two wheels with their spindles and bearings, and if the bearing fric- 
tion was taken into consideration, the efficiency of such gearing would 
certainly not have reached the above-mentioned figure of 94% per cent 
at full load. These figures, of course, seem very high for the efficiency 
of worm gearing. They were published in Machinebt, December, 1903, 
having been obtained from a reliable source, and were never chal- 





Third Edition 


Drafting-Room System, by Ralph E. Flanders - 3 

Tracing, Lettering and Mounting, by I. G. Bayley 17 

Card Index Systems, by A. L. Valentine, J. S. 
. Watts and A. B. Howk 34 

Copyright, 1910. Tin* InduKtrial Tn'Bs. Publishers of MAnnxERT, 
49-55 Lafayette Street. New York City 



by these nicknames. Then each separate part is given a serial num- 
ber. Thus ''L20-49" might mean the head cone gear for a 20-inch 
lathe. This designation would be marked on the pattern and serve as 
a pattern number as well. 

The arrangement of the parts in order for numbering depends on 
whether the parts are to be manufactured and fitted in assembling, or 
fitted each to the other in the process of making. We may take it for 
granted that the shop is trying at least to do business in a profitable 
way, so the arrangement will be considered from a manufacturing 
standpoint. The parts should then be grouped in such manner that 
pieces having similar operations involved will be detailed on the 
same sheets. First will come the large castings, like the beds, legs, 
tables, heads, etc.; after, come the other small castings, involving 
milling and drilling mostly, as the brackets, levers, braces, gear guards, 


" SIZE - 36" X 24" 


*T" Size 

9"x 12" 

"L^- Si2e-I8"xl2" 

Flff. 1. Standard Sise Drawing Bheeta 

etc.; then the castings which are finished mostly by turning, like 
pulleys, gears, and bronze bushings. Next comes the group which 
includes the turned parts made from stock or forgings, such as spin- 
dles, shafts, steel gears, etc.; followed by a group of the small parts 
made on the screw machine. The last class contains the parts made 
by milling and drilling from flat and rectangular stock. If the parts 
are numbered and arranged on the drawings in some such order as 
this, the workman who makes a specialty of certain operations will 
have all his work conveniently grouped together on the sheets. 

Standard Drawing Sizes 

To obtain the greatest simplicity in handling and indexing in the 
drawing office, it is necessary to have a single standard size for the 
sheets. In the shop, however, big blueprints are a nuisance, and the 
sheets should be no larger than is needed to show a convenient num- 
ber of the parts in the group being detailed. It is possible to satisfy 
the requirements of both shop and office by making the tracings of a 


Bt&ndard size, and cutting the prints up afterward into as manr 
smaller sheeta as may be necessary. Fig. 1 shows bow the conTenlent 
38-lnch hj 24-lnch "D" size sheet may be cut up Into the other smaller 
sizes; thus it may make two "H" sheets, or tour "L" sheets, or eight 
"F* sheets, or two "L" sheets and four "P" sheets, and bo on. The 
smaller size Is especially suitable for the parts made on the screw 
machine. I9an extra large sheet is needed' for an assembly, or a full- 
■lie Ttew of a large casting, a 36-lncb by 4g-inch sheet, or larger, may 
be made, folded Into the standard sheet dimensions, and filed with tbe 


Starting In the order fn which the parts have been grouped, detail 

them out on large sheets, sub-divided to suit the case in band. Don't 

try to crowd them, but give plenty of room tor changes and additions, 
and leave space in each drawing for adding other parts of a similar 
group, if this ebould be required In the future The lower right-hand 
comer of each secllon Is ruled off Into a title as shown In Fig. 2, con- 
taining on the top line the symbol of the machine. In this case B3, 
which means No. 3 plain miller, then the lot number, which la Hlled In 
on the print, and lastly, the list of part numbers included on that 
drawing. The second line contains in large letters a title descriptive 
of the contents of that drawing; the next names the machine, and 
after that comes the firm name and the space for initials and dates. 
The column at the right, headed "Changes.'' will be explained later on. 
In assigning numbers to (he parts, leave a few numbers out at the 
start to give to the assembled drawings when they are made. Be^ln 
by numbering the column, say. No. 15. Leave out two or three num- 
bers, to give leeway, if it Is desired to add any new details to that 
Sheet later on, and then number the knee and saddle, for instance. If 
they come next, 19 and 20. The first sheet then would include Nob. 
IS to 18, and so l.i-lS would be printed In the proper space In the 
top line. The drawing with the knee and saddle, containing only these 



two details might be numbered 19-23, and so on. In the same manner, 
if the first group ends at 60. begin the next group at 100; that might 
end at 271 and the next begin at 300, and so on. Thus parts and draw- 
ing will be numbered in a flexible way which will make additions easy 
without deranging the list of parts. In the margin at the lower right- 
hand corner of the sheets should be placed the numbers inclusive of 
all the details on all the drawings of that sheet, as showt in the sam- 
ple title. Fig. 2. This is for convenience in filing the tracings. 


In detailing, the way in which the parts are dimensioned, the com- 
pleteness of the information given by the dimensions and the notes, 

Vi« X Vm Kcjrwajr 



Plff. 8. Detail Drawing 

and the clearness of the drawing itself, all these points together make 
the difference between help and hindrance. Much has been written in 
mechanical papers, and much more said in the shop, profanely and 
otherwise, about the dimensioning of drawings. The draftsman must 
keep in his mind's eye the whole course of the manufacture of the 
piece, and give the dimensions in such manner that the workman will 
not have to add or subtract or multiply or divide this and that to 
obtain the measurement he requires. Of course no scaling of draw- 
ings is allowed in the shop. The ideal to be kept in mind is that of 
a drawing having information so completely given that the waytering 
man, though a fool, need not ask questions, but take the blueprint, 
follow it in blind confidence, and turn out work all completed save for 




are shown for all the diameters. The determination of limiU calls 
for good Judgment on the part of the draftsman. It is very natural 
for him to put the standard much too high, while the shop often com- 
plains of the closeness called for, not realizing that by the old cut- 
and-flt method much closer work was done than is needed or called 
for under the limit system. Limits may be expressed in two ways. 
For instance, a running fit on a shaft to go«in a 1%-inch standard hole 
in a bronze box may be marked 1^ 

or it may be expressed 

— 0.001 max. 
—0.0015 min. 


The first way may be best for shops where the workmen have not* 
yet become acquainted with their micrometers, but it savors strongly 
of the "% inch plus 1/32 inch less % of 1/64 inch" of our forefathers. 






Fig. 4. Another Example of Detail Drawing 

In the better shops of the country the very errand boys learn to use 
the micrometer with ease and skill, so it would seem that the second 
method of marking the size ought not to puzzle the workmen very 
long. In either case the larger dimensions should be on top, to catch 
the eye first. In places where there are no limits given, of course it 
Is understood that good, accurate scale measurement will do. 

On the drawing, the tap drill size and the depth of a tapped hole 
are shown. The two Journals are marked "Grind," which means 
"grind to size"; the one into a plainly, shown recess, the other, where 
the box does not come within i{, inch of the shoulder, up to the fillet. 
In general it is intended that the dimensions shall be so arranged that 
the lathe hand will be able to use them as they stand, without bother- 
some calculation. On work made from the round or rectangular bar, 
finish marks are omitted. If it is desired that the piece be left rough 
at any point, the words "stock size" may be applied to the figures 
descx*ibing that dimension. For Instance, on a 1^4 -Inch cold-rolled 
shaft turned up for a short distance at each end, the central part 
would be dimensioned 1^-lnch "stock size." This particular piece is 
used twice in the construction of the machine, and in diCTerent locali- 
ties, so it is given two names under the same part number. 


Part Llsta 
Two lists are required: A Hat of detailed parts, and u llet of stock 
partB. Gver7 single Item of a given machine must. be recorded some- 
where, eltber on the blueprints or In the llet of screws, uasbers and 
other sundries taken from the stock-room or purchased outside. A 
page heading for the list at parts In the casting group Is shown, upper 
sketch. Fig. 5. The first column gives the part number; then comes 
the name, then the number wanted, the material of which ther ar« 
cast, and lastly, two columns marked "castings ordered'' and "order 
Blled." These spaces may be conveniently checked by the one wtio 
orders the castings, and he will thua have a good Idea at any time 
of what progress la being made in supplying the needed material. 
This does not, of course, take the place ol whatever foundry order 
system may now be in use. The page heading ot the parts made front 
the bar and rod are also self-explanatory, the last two columns being 
filled in with the dimensions of the rough stock needed to make each 
piece. It will be remembered that numerous blank spaces were left 


Mb. a 

In numbering the jiaits, to give room for future changes. Similar gaps . 
should be left in the list of parts. 

The "List of Stock Parts," of which two sample headings are ahoivn. 
Fig. 6. covers everything not otherwise provided for. and gives all the 
information necessary for ordering. Leave plenty of room here, as 
well, for additions and alterations. These lists may be done In ink 
on printed and ruled blanks of thin bond paper, or they may be type- 
written for blueprinting in the foUonlng manner: Do the work In a 
good strong manifolding machine with a new black ribbon. A piece 
of carbon paper should he placed In back of the sheet with the face 
against it. This prims ih>^ back of the sheet as well as the front.. 
and makes characters heavy enough to make good blueprints. 

If these lietB are printed, clipped together in tough paper covers, and 
distributed generally among ihose who have any use for them, they 
will save a vast amount ot useless mental strain. Before a new lot of 
machines Is ordered, the stock-keeper can go through the list and see 


tbst he has got every acrew and washer on hand that Is needed. Tha 
man who ordera the castings can look over the supply on hand and 
goTem himself accordingly. The man who has charge of the har stock 
can keep blmaelf supplied with the necessary material, and cut It off 
ol the proper croSB-sectidn to the proper length, as fast as It Is needed. 
The foremen in the shop can assure themselves that nothing has been 
forgotten, that everything Is coming along as It is wanted, and have 
In general a constant reminder at hand of what Is required of them. 
ABBembly Views 
After all this has been done, we may make the necessary assemblf 
views, working cntti-ely from our detail views and stock part list 
It the parts all go together aa required. It Is an Indication that the 
Job will check up well. On these drawings, at least, and perhaps on 
the details. It Is a good plan to use some simple method for distin- 
guishing the various classes of materials by cross-sectioning. It is 

List of 5q Htao Set Screws. 



S-off'* Btlhnu ■ mada IndltiS- FinHhiat-lA'iy'd». 

|9«-7« tMlHi, 

S'nqlt BUhna ■ FirsI Oi/ahiv - nVida. 

«« J 

RovrtH Btif - 'i.'aam.Far!>,ihtcl-:mOii4J:'<qi. 


2i&.rt 1 

good enough to have one style for steel and wrought iron, one tor 
braes, bearing meUls. etc., and one for cast and malleable iron. 

Next conies the tracing. II the machine te a new one. never built 
before, it Is a good plan to shellac the paper drawings and send them 
out Into the shop lor the first lot. This will make the InevlUble 
changes easier to handle than when blueprints are used from the start. 
As soon as the machine is well In hand, the drawings may be recalled, 
cleaned with alcohol, and traced. It Is of great Importance to uae the 
very best grade of tracing cloth. Not every well-advertised brand will 
stand the rubbing and scrubbing for a dratteman who has the fever 
of Improvement seething In his brain. U costa much less to get the 
best tracing cloth at the start than it does to have to make new trac- 
ings on account of having cloth that will not stand erasure. 

The checking may now be done. It Is best to delay this until att«r 
the tracings are completed, and then it la done once tor all; and tt 


•can best be done by some one other than the man who did the detail- 
ing. If, however, it be gone over in some orderly, systematic way, it 
may be as well done in a one-man drafting-room as in some large 
establishments, where the drawings are examined and initialed by 
«very one in sight, from the engineer in charge down to the tracer. 

Think over beforehand every direction in which a mistake is liable 
to occur, and make a table covering these chances of errors and tack it 
in plain sight on the wall over the desk. For such a system as that 
we are considering, the following list might be appropriate: 

1. General design. 

2. Finish. 

3. Dimensions; sufficiency and arrangement. 

4. Dimensions; compared for accuracy. 

5. Compare with list of parts. 

6. Compare with list of stock parts. 

7. Pattern number. 

8. Notes. 

9. General title. 

That is to say, beginning with the first part in the list of detailed 
parts, we would examine it first for points in its general design. 1. Is 
it well proportioned, strong enough, and in general harmony with the 
lines of the rest of the machine? Could it be changed so as to require 
less machining, or to make it cheaper to mold (if a casting)? 2. Is 
there any unnecessary finish, and has the needed finish been properly 
indicated? 3. See that the dimensions are sufficiently full, and 
arranged in such manner that the workman will know, without figur- 
ing, the dimensions he needs. 4. Compare the dimensions of the detail 
in hand with those of every single contiguous and related piece in the 
whole machine, whether detailed or given in the list of stock parts. 
This is the important item in the list, and if it is faithfully carried 
out, it will double-check every dimension, as each part is thus checked 
up once individually, and again in the checking of other related parts. 
5. Compare titles and stock dimensions with entries in the list of 
detailed parts. 6. See that every stock part which is related to the 
detail being considered is properly entered on its list. 7. If the detail 
is a casting which has no pattern of its own, but uses that of some 
other part of the same or another machine, see that the proper pat- 
tern number is given under the title. 8. Be sure that notes are given, 
to supply the workman with all the information he needs as to fit, 
finish, etc. Otherwise he will worry the foreman with fool questions. 
9. After the details have been checked, as above, see to it that the title 
of the drawing is correct as to part numbers, names, etc. 

In the same manner the lists must be gone over, checking every 
name, number, note and dimension. 

Printing, Mounting, Etc 

The tracings may now be blueprinted, cut up into the proper sec- 
tions, and mounted on suitable boards. Do not send them out rolled 
up, to get defaced and torn, and refuse to lie flat in the files, when 


they are returned. When mounted, they are distributed to whoever 
needs them. With the details intelligently grouped as described above, 
and with not too many on a drawing, one set of detail prints ought to 
suffice to put through a single lot in the shop. Be generous with the 
lists, however, and put them wherever they can be of any service. 
Stamp each print, in red, with the date when it was printed, and keep 
a record of prints made and delivered to the shop. This record will 
be found very valuable when making changes as described below. 


In a shop which is alive, the product is in constant process of im- 
provement, so it is necessary to make a full provision for this state of 
affairs in a good drafting-room system. In the first place, the men in 
the shop should on no condition be allowed to make an erasure or 
addition of any kind to the shop prints and drawings. If an error is 
discovered or an improvement found advisable, let it be reported at 
once to the draftsman, who should stand ready to make any needed 
change with promptness and good grace. In general practice, however, 
it will be found best, from the drafting-room standpoint and that of 
cheapness of production as well, to delay radical changes until a new 
lot is begun. In some places the foremen and other prominent men 
are furnished with stub books in which they write suggestions for 
the improvement of the different lines of machinery. The leaf is filled 
out in duplicate with the stub, and sent to the drafting-room, where 
it is considered either immediately or when a new lot is ordered, 
according to the urgency of the case. This scheme gives the drafts- 
man the advantage of having all the suggestions in a tangible form, 
for ready reference, and also gives the credit to the men who hold 
the duplicate stubs. 

In the same manner as was done when c'lecking, it will be found 
advisable to make out a list of everything v\ hich might require atten- 
tion in making alterations of any kind. The following table would 
cover about everything. This ought also to be printed and nailed on 
the wall in plain sight of the draftsman: 

1. Detail tracings. 

2. Assembly tracings. 

3. List tracings. 

4. All prints (detail, assembly and lists). 

5. Patterns. 

6. Special tools. 

7. Record of changes. 

In making a change, if it is at all elaborate, it is safest to sketch 
it out on detail paper before making changes on the tracing. In eras- 
ing tracings, use any smooth sand eraser which has been approved by 
experience, and place under the part being treated a sheet of some 
smooth hard substance like celluloid, sheet metal, or a round-edged 
piece of glass. This will remove the ink without giving the rubber a 
chance to deeply abrade the cloth itself. Cases sometimes occur in 
which a comparatively simple change, like shortening the over-all 


length of a complicated casting, would entail a considerable amount of 
labor. To avoid this, the dimensions only may be changed, and then 
a small heavy circle drawn around each dimension. If on a paper 
drawing, draw the circle with red ink; if on a tracing, use black ink. 
This gives notice to whomsoever it may concern that the dimensions 
are out of scale, so that the drawing will not measure correctly. Where 
the change is one of 1/32 inch or less, it is not advisable to alter the 
lines of the detail or circle the figures. 

The assembled drawings should be kept up to date if they are to 
serve any purpose at all. In some cases it might be permissible to 
introduce circled dimensions on these tracings as well, where an other- 
wise small change would require much erasing. The lists also must 
be corrected, of course. 

There are two ways of changing the blueprints, where the change is 
so small as to make a new print inadvisable. One way is to use the 
"soda solution" which acts chemically on the paper itself. This gives 
the most permanent results, but requires some skill in handling, as 
the lines do not appear until some time after the liquid has been 
applied. Chinese white, ground in water, can be used like ink, and 
easily removed when desired — so easily, in fact, that it is best to shel- 
lac the changed portion of the print to preserve the lines. With either 
method it is best to -draw in the new^ lines first, and then obliterate 
the old ones with a blue pencil, this being the only known method of 
erasing on a blueprint. Be sure that every print of each tracing is 
changed — the list of prints charged should take care of this. If new 
copies of a print are required on a change, destroy the old ones; do 
not leave them lying around, to cause trouble. 

Patterns and special tools must be looked up for each individual 
case, and duplicate written orders made out for changes, one to go to 
the toolmaker or patternmaker, and the other to be kept in the office 
as a record until the work is reported finished. 

Referring again to Fig. 2, there is shown at the right of the title a 
column headed "Changes." After each change is completed and 
checked up, the person making the change should enter here his 
initials and the date, in small legible characters. A "Record of 
Changes" book should be kept. Under the date signed in the 
"Changes" column there should be entered a brief description of the 
alterations, giving exact dimensions, and perhaps the reason for them 
as well. A separate book should be kept for each line of machines 
manufactured. By comparing the last change date on a print with 
that on a tracing, it can Immediately be determined whether or not 
the print is up to date. By referring to the given date in the "Record 
of Changes," the exact scope of the alteration can be found at any 
time. This will be found a great convenience. 

In cases where an error has been made in the shop on a machine, 
and a deviation from the drawings in that particular case will save 
a large amount of costly labor and material, such change may be made; 
but it must be recorded, for convenience in making future repairs and 
attachments. It is the proper thing to number the machines of a 


given kind and size serially, beginning, for instance, by numbering the 
first 20-inch lathe built, No. 1. the next one No. 2, and the one hundred 
and seventy-eighth one No. 178, and so on, as long as the machines 
are built. This number should be stamped in a prominent place, and 
attention called to it in the catalogues and other printed matter of the 
firm. A book for a "Record of Machines Shipped" should be kept, 
with a page for each individual machine. This page Is numbered wltb 
the tool's serial number, and contains name of person or firm to whom 
the machine was sold, a record of the inspector's tests, a description of 
any change from the standard drawings used on other machines in the 
saif^e lot, and a record of all utlachments furnished, repair parts sent, 
complaints from user, etc. It is easy to see the value of such a record 
as this in furnishing new parts, remedying defects, and estimating the 
values of various designs. 

After each lot of machines has been approved ready to ship, all the 
prints — detail, assembly, and lists — should be returned to the office. A 
complete set should be taken from them and the duplicates destroyed. 
File this set of blueprints away in a folio the size of the *'H" sheet, 
doubling the "D" size to do this. As far as the work done in the 
home shop is concerned, this, with the office book, will furnish a rec- 
ord of each individual machine for all time, no matter whether it goe» 
to Klondyke. or stays in the town where it was made. These folioe 
should be kept indefinitely. 

Drawing's for Jigs and Fixtures 

It is not feasible to try to make the tool drawings of jigs, special 
cutters, etc., on full-size sheet, even though divided, as the standard 
parts are. These should be made on a suitable standard size of a good 
grade of detail paper in a quick, sketchy way, shellaced, and sent into- 
the shop. Number these drawings with the symbol and part number 
of the detail for whose manufacture they are used, adding a serial 
number as well. This serial numbering is common to all tools made, 
no matter for what purpose, and is to be given them in the order the 
drawings come from the office. Thus if L 22-75 is the part number for 
the spindle of the No. 4 vertical miller, the finishing taper reamer for 
thie hole in the same might be numbered L 22-75-193. If A 4-267 is the 
index worm-wheel for the No. 4 universal miller, and the next toot 
drawing made is a hob for same, it would be numbered A 4-267-194. 
These numbers should be stamped or etched on the different tools as 
soon as they are made. 

A book should be ruled up for a "List of Tools." A sample page 
heading is shown for this in Fig. 7. The tools are entered serially as- 
fast as drawn. The first column gives the date when drawn, the main 
part of the page, the description. Next is a space for a list of parta 
for which this tool is used other than the one it was made for. As 
changes are made, old numbers are crossed ofT from here and new ones 
added, so plenty of space must be allowed. For convenience in finding 
the drawing, the last column gives the standard size of sheet on which. 
the tool was drawn. It will be noted that one tool is marked "None." 



This tool was made in the shop off-hand, without any drawing to go 
by, but it was entered on the list, and its tool number marked on it, to 
gire it a local habitation and a name. These tools and Jig sheets 
should be filed in a drawer of their own, divided into compartments of 
suitable size, and all arranged with serial numbers in order, the lowest 
at the bottom. The jigs and tools themselves are best arranged with 
the serial numbers in order, since they will avoid constant rearrang- 
ing as the stock increases. To find them readily, an index list should 
be prepared, giving the standard machine parts in numerical order, 
and listing under each one all the special tools used in its production, 
whether those tools were originally used for it or not. Of course much 
of this system of keeping track of special tools is required only in 
shops where they are used in large numbers, but that may be taken 
for granted, if the concern is in earnest about doing a profitable busi- 
ness on a large scale. 

Special Machines and Attachments 

In cases of special machines or outside work of any kind, which does 
not come under the head of standard product, the same system may 

Date Tool No 

2f7-04iH/4 7e-27e 


2 17-04 iB2- 26-277 

2-/8-04 (B?- 23- 278 

2-20- 04 \Ln 400-279 


.4^8 Jtffli. (Kia/rT\jt\, fox. 

4u.^y\g. Jjr{u,^rnA^^t/ltuiir 

c^/% *\a . (RouAy ^AAjttlt^ 

■4<ru ^ZJujOJojck' 

Used also for 


{H7-96) <Ht72j(LU472j 

(0 2-49) (H6 8ZJ (L 17-24) 

(120-460) (/LU-4eO) 


MdCHtNtftY N r 

Fljr. 7. List of Tools 

be followed as a whole, with the exception of the symbol for the ma- 
chine, which should be given a serial number instead of the letter and 
size number of the regular product. A record of these serial numbers 
should be kept in the office, and the drawings filed away, if the Job is 
important, in the same manner as the standard blueprints. Attach- 
ments to regular machines, made up separately, may follow the entire 
sjrstem for standard parts. The symbol describing them may be 
formed by adding a letter to the symbol letter of the machine. Thus 
AA-3 would be "Vertical Milling Attachment for No. 3 Universal 
Miller"; BD-4 would be "Rack Cutting Attachment for No. 4 Plain 
Miller," etc. 

In place of the record books suggested, it might be better to use 
loose leaves, with punched holes, held in suitable binders. These 
teftTes could then have proper entries made on them on the typewriter. 


and thus save hand work. It will be noted that in no case are there 
any forms used in such numbers as to require the use of printed mat- 
ter, so the Initial expense is small. Printed forms, index systems, etc., 
may be evolved as the shop grows. 

Summary of Advantaflres of System Outlined 

In recapitulation, a drawing office managed in some such way aa 
this will give the firm the benefit of the following advantages: 

Complete tracings and blueprints, easily filed and indexed, and made 
in such a way as to give the fullest, clearest information possible to 
the workman. 

Complete list of parts as a convenience in tracing the progress of 
the work and keeping up the supply of raw material. 

Complete list of all stock parts, for the benefit of the assembling 
foreman and the stock-keeper. 

A list of all tools used for any given part, and ready means for find- 
ing the same, also means for ordering duplicate tools by number from 
the original drawings. 

Means for making all changes entailed by changes in the product in 
a simple, comprehensive way, and for making a permanent record of 

A record of the suggestions made in the shop and office, for the 
drafting-room in making changes, and for the firm in determining th« 
relative value of their employes. 

A full individual history, by means of the office record and the filed 
prints, of each machine built, useful in many obvious ways. 

There are many men to whom the suggestions given above will 
seem the veritable A B C of the business; on the other hand, there 
are dozens of places where the suggestion of doing things in some 
such way as this would be considered a dangerous and revolutionary 
proposition. But practically all the work covered by a good system 
has to be done by someone, some time, and if it Is not done decently 
and in order, it will be done in vexation of spirit, and with waste of 
time and money. 



While the previous chapter has dealt with the systfem of the drafting- 
room in its relation to the shop, and outlined its functions in a gen- 
eral, although comprehensive, manner, the present chapter is intended 
to deal with the small details of performing the work in the drafting- 
room, at the same time as many valuable hints are included with spe- 
cial reference to the young draftsman. In fact, the present chapter 
has, in particular, been addressed to the beginner, although it has 
general application. 

At the commencement of a drawing-office career only a few^ tools 
may be purchased, adding others as they are needed. Careful selec* 
tion is necessary, and good instruments pay for themselves in the end. 
A set of drawing instruments comprising a straight pen or two— one 
for black and one for red ink — a spring-bow pen, bow pencil, and divid- 
ers, a six-inch compass with fixed needle-points and interchangeable 
pen, pencil, and lengthening bar, will suffice. T-square, triangles, pen* 
cils, rubbers, erasers, and pens are usually provided by the office. Each 
man should keep his own instruments, and have a private mark on 
his triangles, scales and T-square for identification in case they become 

Small instruments should be put away each night, as in cleaning up 
the office they are easily lost. A drawer or cupboard with trays or 
boxes for the various. tools is very necessary for the draftsman. A 
large clean rag duster or brush to wipe the board and T-square occa- 
sionally should be provided, as the least particle of dust getting into 
the pen will (Clog the ink, causing a poor line to be drawn. In case 
the eraser must be used (a thing to avoid as much as possible) rub 
a little French chalk or soapstone well into the part erased. A little 
of this prepared chalk should always be kept on hand; it can be pro- 
cured from any artists* material store. A piece of rag, cheesecloth 
or chamois skin hung by a thumb-tack at the end of the drawing board 
comes in handy for wiping the pens. A sand-paper pencil sharpener 
and an oil stone completes the list. 


Too much cannot be said about the inks used, as I believe to a cer- 
tain extent a great many bad tracings can be laid to the bad quality 
of ink used in the various drawing offices visited by the author, fn 
this country and abroad. 

Good ink is indispensable, and no one should attempt to make a 
tracing until he has it. Some offices, to save (?) expense, resort to 
many ingenious ways of making ink by wholesale. A large bottle 

• Machinfrt, SJeptembcr, October, November. 1906. 


with a ground-glass stopper is provided. A quantity of broken Ink 
(which can be purchased by the pound and much cheaper than buying 
by the stick or cake) is put into the bottle; a quart or so of ammonia 
is then poured over the ink. The bottle is then put in a warm place, 
shaken every now and then until the ink is dissolved, or partly so (the 
latter usually being the case) when it is supposed to be ready for use. 
This is the cheapest and worst way of making ink. Some drawing 
offices buy the ink ready mixed, put up in pint or quart bottles. For 
shop tracings, either of these methods may be resorted to. But for 
neat work it is almost impossible to get along with either; the only 
way is to mix the ink fresh each morning, washing out the pallet 
every day. When purchasing the ink stick, the very best should be 
bought; it can be recognized by a pleasant odor which cannot be mis- 
taken and is perceptible when grinding it in the saucer. The saucer, 
or pallet, should be spotlessly clean, and the water clear. Do not 
use too much water at first; more can be added as the ink is mixed. 
A little vinegar in the ink will keep away the flies. In many offices 
in warm climates they are a great nuisance; the writer has seen whole 
views completely eaten away by these pests in a very short time. 
Commence by rubbing a little Prussian blue in the saucer; this is not 
absolutely necessary, but it Improves the ink somewhat and helps to 
thicken it quicker. Saucers made of slate with ground-glass covers 
are the best. The ink stick should be held firmly, but do not bear too 
hard upon it while grinding, or else, when mixed, the ink will be 
gritty. Grind until the bottom of the saucer cannot be seen when 
blowing down into the ink; this is a good test, and one can also see if 
the ink looks gritty. Try it on the edge of the tracing cloth or paper 
to see if it gives a clear black line. The cover should always be kept 
over the ink to keep it from evaporating and free from dust. In cold 
weather, if the ink should thicken, hold it before the fire or heater, 
when it will run easily and will not clog the pen. 

Ordinary scarlet ink is used by. some draftsmen for making red lines, 
although it is much better to use a mixed ink of crimson lake color, 
adding a little ox-gall to make it run. The prepared ox-gall in tiny 
Jars can be procured from artists' material stores. In the absence of 
this, a little soap rubbed into the color will answer the purpose. Bi- 
chromate of potash dissolved in the water before mixing the ink will 
help to keep away flies. 

It sometimes happens that draftsmen are troubled with sweaty hands 
which mark the tracing as the work proceeds. This can be avoided 
by putting half a teaspoonful of ammonia in the water used for wash- 
ing the hands. 

Truing up the Instruments 

As the pens are constantly used they will become blunt, which can 
be seen by holding them against the light and looking down upon the 
nibs. Every draftsman should be able to set his own instruments. 
There should be an oil stone in every oflice for this purpose. Let It 
lie flat on the window sill or a table near to the light. Screw up the 



nibs tight, and, holding the pen in an upright position between the 
finger and thumb, move it backward and forward, as shown in Fig. 8, 
along. the stone as indicated by the arrows, tilting it from side to side 
as shown by the dotted lines. 

In this way a round and even surface is given to the nibs. They 
will be of the same length and true with each other. Now, holding 
the pen in a slanting position of about 30 degrees, rub the nibs upon 
the stone in a circular direction, as indicated in Fig. 9, rolling the p€n 
as It were between the thumb and finger, turning It over and grinding 
both nibs alike. Hold the pen to the light occasionally to see if the 
nibs are level, and look down upon the points to see if the flat sur- 

— •■ » 


Flffs. 8 and 9. Truing: the Point of the Pen 

faces have been taken out. If sharpened correctly, one will not be 
able to see anything, the same as when looking down upon the edge 
of a razor. 

The thumbscrew must now be taken out and the inside edge of the 
pen be rubbed across the oil stone several times. Thoroughly clean 
the pen from any grit or oil and try it upon the edge of the tracing. 
If too sharp, it will have a tendency to run away from the T-square 
or straight-edge, in which case it should be rubbed on the stone again, 
as in Fig. 8, though with care, as all pens should be fairly sharp. The 
bow pen is trued up in the same way, with the exception that a thin 
slip of stone is passed between the nibs to take off any rough parts, 
as the nibs of the bow pen do not hinge; and when straight pens are 
made in the same w^ay, they should also be treated in the same man- 
ner. All instruments should have the best of care. When not in use 
for some time they should be kept clean and free from rust by wiping 
them on a piece of chamois leather greased with vaseline. 


Traoinsr Paper 

Tracing paper is much used in architects' offices and occasionally 
by engineers for pencil sketching. When it is used for permanent 
work, the best quality should be had. But although it is possible to 
purchase paper capable of standing fairly rough usage, it is by no 
means as good as cloth. 

A narrow strip of tracing cloth tacked along the lower edge protects 
the paper from being torn while leaning over the board. Either 
thumb-tacks, copper tacks, or small carpet tacks may be used to hold 
down the paper; a small magnetized hammer can be used for the lat- 
ter, picking the tacks up very quickly, so that whichever plan is 
adopted, it takes about the same time. In case the tracing will be 
worked on for some time, or if there is any coloring to be done, the 
paper must be mounted on the board as described later. 

Tracing Cloth 

For permanent work tracing cloth should by all means be used. 
Cloth is either glazed or unglazed, the foreign make being by far the 
best. With proper care a tracing may be taken up when complete, 
as clean as when cut from the roll. All shop or working tracings 
should be made on the unglazed or dull side of the cloth, as this side 
will take pencil lines nicely, and when erasing has to be done it will 
not mar the surface so perceptibly. But for show or estimate trac- 
ings, where much finer and neater work is required, the glazed side 
must be used. The lines will be sharper, and the work will stand out 
much better. In either case the cloth should be laid down in the same 
manner as the paper. It should then be rubbed down with pulverized 


Laying Down the Tracing 

The drawing to be traced is squared up with the board and wiped 
down with a dry cloth or duster. The roll of tracing cloth is run 
down the board and cut off to correct size. The. edges at either side 
are then torn oft quickly and the cloth is laid down correct side up. 
A tack is put in the center of the top edge; the flat of the hand is 
drawn firmly but gently down to an opposite point at the lower edge, 
the fingers spread apart, while another tack driven between them 
holds that edge. Run the flat of the hand gently to the one side, driv- 
ing in a tack; then to the opposite, stretching it well and securing it 
by another tack. The four corners and all intermediate spaces are 
then held down in the same manner. 

With a dry rag or piece of chamois skin rub some pulverized chalk 
(or chalk scraped from the stick) all over the tracing cloth, dusting it 
off with a dry rag or brush. This will cause the pen to bite much 
better, especially in the case of show tracings where the glazed side 
is used. Some draftsmen use a little ox-gall in their ink for this pur- 
pose, but unless the exact quantity is used, the ink will be very sensi- 


Everything is now ready for tracing. Try to understand the work 
as you proceed. If th« job is likely to last long, work on one view 


they should not be moved; for this reason some pens have small lock 
nuts on the thumbscrews. They should be wiped and the ink put 
in without again adjusting the screw. This particularly applies when 
making heavy lines. In this way all lines will be of the proper thick- 
ness. The pens can be filled with an ordinary writing pen or dipped 

in the ink sideways. 

Working Tracings 

Working tracings or shop tracings are usually made a little heavier 
than others. The lines should be all of the same thickness. No red 
or blue lines need be used, but all black, and although the tracings 
should be neat, especial care being given to the figures and dimension 
lines, yet such care need not be taken as when making a show or esti- 
mate tracing. The figures should be plain and simple and might be 
made a little large. The arrow points should be true and go exactly to 
their intended position. The figures should be checked before hand- 
ing in the tracing so that as few mistakes as possible will come back 

to the tracer. 

Show Tracings 

Estimate or show tracings should have a little more time expended 
upon them. The lines need not be so heavy and as a general rule are 
shaded, t. e., the lines furthest from the light, which is supposed to 
come from the top left-hand corner, should be heavier than the others; 
this is clearly shown in Fig. 12. Shade lines can be made by going 
over the lines again or adjusting the screw of the pen, causing the ink 
to make a heavier line. When dark-lining a circle the radius is kept, 
but the center changed slightly, as shown in Fig. 11; or the same 
center and radius may be kept, going over the dark or shaded side sev- 
eral times with the pen. 

The letters, figures and dimension lines should be made neatly, the 
arrow points evenly made. Some draftsmen put in the arrow heads 
with their spring bow pen, and since they can be put in Just as quickly 
this way and look much neater it would be well to practice this method. 
Dotted lines should be finer than full ones. The dots and spaces 
should be made the same length — about one-thirty-second to one-six- 
teenth inch in length. In shading rivet heads sometimes a small half 
circle is made inside the first, as shown in Fig. 12. It should be 
heavier than the outline of the rivet head. 

The heading or title should be neat and attractive and a fancy bor- 
der line might be made. All notes or stray words should have a neat 
red line drawn under them. Bolt heads should be neatly made and 
all small work carefully executed. Threads of bolts should be parallel 
and equally spaced, and may be accurately drawn or indicated, as 
shown in Fig. 13, c, d and e. Dotiea work can be shown to advan- 
tage if the dots forming the apex and root of the threads are united, 
as shown at e. These may seem trifles, but they all tend to make a 

neat tracing. 

Holding the Instruments 

The author has been more than surprised at the rough and unsteady 
way which some draftsmen have of holding their instruments. The 


No. . 


only, trusting to the eye for correct spacing. Section lining done this 
way looks very neat and even. Another section liner, shown In Fig. 
16. can be made to fit triangles having a recess in the center. 

VlewB In section are sometimes colored, generally on the back, turn- 
ing the tracing over and tacking It down again; or, where there Is 
much coloring to be done, tbe tracing should be mounted as described 
under that head at the end of this chapter; otherwise the color will 

—i tmuMrMw — 

cause the tracing to buckle, giving It a very untidy appearance. Hav- 
ing stretched the tracing, one may be mixing the colors while It thor- 
oughly dries. The colors should be rather thin, and to make them run 
evenly a little prepared ox-gall should be mixed In well with them. 
This should not be omitted, as otherwise the colors will present a very 
smudgy appearance. Some draftsmen use a small piece ot soap In 
place of the ox-gall. 

By trying the colors upon a scrap piece of tracing cloth or paper 
and turning It over, the proper shade may be obtained. 

■>fVmy.un "diS^Jr^rm 

adopted stnndaril tor croHa-aecttonliig tor tb* puppose 

vtT. croas-stctlonlrg Blone should never bo dependwl 

vpntlons uspd In deelgnstl 



Following is a list of representative colors used in many offices: 

Cast Iron Payne's gray. 

Wrought iron Prussian blue. 

Steel Crimson lake and small quantity of blue. 

Brass Yellow. 

Copper Crimson lake and yellow. 

Brick Crimson lake. 

Wood Burnt sienna. 

Earth Daubs of ink, Payne's gray, etc. 

In the absence of Payne's gray, a pale wash of India ink in which 
has been mixed a little Prussian blue may be substituted. Very neat 





Fig. 19 




Fig. 18. 




Fig. 15 

Fig. 16 

Fig. 20. 




Fiffs. 16 to 20 

sectioning can be made with crayoDs, toning them down with a soft 

Dimensions and Center Lines 

Working tracings should have the dimension lines, center lines and 
all lines black ink, the idea being to make a neat, distinct tracing for 
use only, whereas a show or estimate tracing should be made with 
greater care. It is a well-known fact that many contracts have been 
awarded on the merits of a well-executed piece of work by the drafts- 
man. The time and expense spent upon making a neat show tracing 
is never lost. Make the center lines of red ink or color, a fine long 
dash and dot line; make dimension lines either one continuous line 
broken only where the figures come, or a dash and dot line, as in Fig. 17. 



Border and Cuttlnflr-off Lines 

Simple as these may seem, yet many well-executed tracings have 
been spoiled by either neglecting a border line or making a very 
poor one. A one-line border is perhaps the best and its thickness 
should match the work in hand, together with the size of the sheet. 
There should be plenty of margin between the border line and the 
work. A fancy border line, of which a few samples are given in Fig. 
18, may be put around estimate or show tracings. The cutting-off 
line should not be too near the border line, say, from % inch to 1 
inch. Nothing looks worse than to see a good tracing spoiled by cut- 






Flga. 21 to 26 

ting off within a quarter of an inch of the border line (compare Figs. 
19 and 20). The initials of the draftsman and date tracing was made 
should not be omitted. 

Miscellaneous Directions 

Attention to details is perhaps the true secret of making a neat 
tracing. No matter how trifling a detail may seem, it should be made 
as neatly as the rest of the work. Channels, angles, etc., in section, 
should be made accurately, as in Fig. 23. Do not make them, as is so 
often done, like Fig. 22. 

When tracing a blueprint, the tracing should be tacked down with few 
tacks, as it will have to be lifted quite often to see the work distinctly; 
in fact, in many cases, it would pay to make a drawing from the blue- 
print and trace it. Drawings which are faint or unfinished should by 
all means be made clear before attempting to trace them, thereby sav- 


ing much patience, but in particular the eyesight. In tracing from 
another tracing, a clean sheet of white drawing paper underneath will 
make it stand out clearly. If the draftsman understands what he is 
tracing, the work will be much easier and he will not be likely to 
make so many mistakes as he would if tracing a number of meaning- 
less lines. 

The tracing should be wiped down occasionally with a clean, dry 
duster or cloth. Cotton sleeves are sometimes used to protect the 
coat. A sponge-rubber or piece of bread may be used to clean a trac- 
ing, but if proper care has been taken, a tracing can be taken up as 
clean and neat as when tacked down. A greased, soiled tracing shows 




?4-36-5l2-74^42. Nos. ZI8-I9-ZO -2 I. 



SCALE 5-r-O" JUNE 6^** I 890. 

f^ff. 26. Bxatnple of Letterinff a Drawlnir Title 

a bad workman. In some offices it is the practice to sponge the trac- 
ings down with benzine. Waterproof ink must be used by all means 
if this plan is adopted. When the tracing is complete, the draftsman 
should look over it carefully, trying to detect any errors, as all such 
count against him. The shop hands, as a rule, are only too pleased to 
point out any trifling mistake coming from the drawing office. Accu- 
racy, as well as neatness and quickness, is desirable. 


No matter how neatly or carefully the working lines of a tracing 
are made, if the lettering and figures are not satisfactory the trac- 
ing will look poor in every sense of the word. The young draftsman 
should, therefore, take especial care to get into a neat way of letter- 
ing, and should devote a little of his spare time each day to this end 
if he wishes to excel as a neat draftsman. Neat letterers are in 
demand and are always sure of a position. Many cases are known, for 
instance, where a good letterer has been employed in his spare time 
to put on the figures and letters of other men's work, and although a 
poor tracing can be improved by neat lettering, to excel in both should 
be everyone's desire. 

A good instruction book on this subject is difficult to find. Most 
alphabet books are ridiculous in the extreme; it would take longer to 
make the letters they describe than the whole tracing. The tracings 
would look insignificant in comparison with the wonderful lettering. 
The letters and figures must conform to the other work — neither 
should be more conspicuous than the other. For this reason it is 


preferable for each man to complete his own tracing. It is an easy 
matter to tell who made the various tracings in most drawing offices 
by the peculiar characteristics of each draftsman — this one by its 
poor lettering or that by a beautiful harmony of lines, letters and 
figures, the whole standing out in correct proportion, fine lines having 
small neat figuring, lettering, and narrow points to match, or heavy 
lines vice versa. Nothing looks more uniform, neater, or is quicker 
done than good, plain, one-line lettering, even for the titles, though 
perhaps a little display may be given to them. 

A few samples are here given. The small letters are for the general 
working parts of the tracings, notes, etc. Headings should be a little 


br^rvcfora/ drai/ghfsmen. T/ies/iydcrrfsha//d/!m(7f/(:&'ff^ssei//tf^^^ 
he gets /nfy a ;fey /mdea^ ymof/e/ferz/jp //e shoM /rat^(X/mk/ly 
f/je/e//isr5 /a^r a/id s^mf//(^r^a/7 fierff j/kum ahg. 


fc^/a/ /e//frj for ^/jha/xf /xa^m^ 

abcdefghijklmnop<^r3/uuy/xy7,. /e345678?o . 

6ENER/7L FLJ^NS ^ — 



— 'S/v/t/? Jayes company — 

^^_ ^^lo. 

Plff. 27. Examples of Letterlnflr 

larger, and the title, which will be referred to later, should be distin- 
guished from the rest of the work by using large letters, either 
blocked out, or capital letters made with a heavier pen. Figures should 
be made plain and simple, without the use of flourish or tail-piece. 
Fractions should be made with one figure immediately over the other, 
instead of to one side. The vertical system of figuring is preferable 
to the slanting, especially with shop tracings. 

For lettering, have plenty of black ink, but not too thick. The best 
kind of pen points are Esterbrook's No. 333, or Gillot's 303 for fine 
work. A heavier pen must be used for titles. Make the letters and 
figures with one stroke of the pen; do not go over them again, but 
get the required thickness, even with titles, by bearing on the pen 


more. A pen can be tempered, when new, by holding it in the flame of 
a match, though pressing it on the thumbnail is generally sufficient. 

Headings or Titles 

The heading or title should be in a conspicuous place, and as far 
from anything which may tend to crowd it as possible. The bottom 
right-hand comer of the sheet is a good place. A heading sometimes 
lopks better without lines drawn underneath, as shown in Fig. 26. 

/ abcdefii^hijklmnopqrstuvwxyT, 





abcdefghijklmnopqrstuvwxyz. \ZZ>a5678Q0. 

Pigr- 28. Alphabets for Lettering on Drawings 

This is entirely optional, however; if lines are put under they should 
not be too close to the letters. Black letters are sometimes used, 
which can be made by drawing six pencil lines equally spaced, as 
shown in Fig. 24. The T-square and triangle are used, and the letters 
can be made quite rapidly. They should afterwards be filled in, or 
one edge of the letters made heavier, acccording to the nature of the 
work in hand. Sloping letters can be made in the same way by using 
an adjustable-headed T-square or a special triangle made for that 


Sometimes headings, letters, flgures and corner pieces are put on 
by means of stencil plates cut out of tin or copper sheets. A stiff, 
short stencil brush is used. The brush is moistened with water, not 
using too much, and is then rubbed along the stick of ink until it 
cannot absorb any more. Particular attention is called to this, as 
here Is where so many fail in making clean and clear stencil work; 
the brush should never be dipped into a saucer of ink, or the ink 
applied with a pen. 


The position for the title having heen settled, pencil lines should 
be drawn on the cloth as a guide for the stenciling. Sometimes the 
title or heading is stenciled upon a spare piece of cloth or paper 
first, then slipped into place under the tracing and the stencil work 
done over it. This is a good plan, as the correct position may thus be 
obtained. If this is not done, the only way is to make a pencil tick 
rr.ark after each letter to indicate the position of the next, as, of 
course, the stencil plate will hide all beneath it except the letter being 
stenciled. Then the letters must each be filled in, as shown in the 
first two letters of Fig. 25. 

Even when the stencil guide referred to is made and slipped into 
place under the tracing cloth, a pencil guide line should be drawn and 
all letters stenciled exactly to it. The pencih lines and ticks are then 
erased. If the brush becomes dry, it may be moistened on the tongue 
without again rubbing it on the ink stick. Draftsmen sometimes cut 
their own stencil plates out of stiff drawing paper, applying a coat of 
varnish on the upper surface. 

Round Writing 

When referring to alphabet books, the writer should have made one 
9XC«ption at least, and that is the round writing system. It is easily 
learned and not soon forgotten. Letters and figures of all sizes and 
shapes can be made by using different graded pens. Books of instruc- 
tion and an assorted box of pens may be had from any stationery store 
of importance. 

Mounting Tr;eicing Paper 

Tracings likely to be in hand a long time should be mounted to the 
drawing board, for several reasons. They will be protected from get- 
ting torn and will not shift on account of the sudden change of tem- 
perature of the room which may take place; they can also be cleaned 
tttitrtt safely than if held by a few tacks. The paper should be cut large 
enough to allow for sticking the edges to the board, and should it be 
frit/rnded to color the tracing with liquid colors, twice the allowance 
should be made, as the paper will be cut after the tracing is made, 
and mounted the second time. The drawing to be traced should be 
laid down square with the board perfectly flat and level, then thor- 
oughly dusted down to remove all obstructions, as these cannot be 
rftfiiovifd after the tracing paper is mounted. 

A long, flat straight-edge with a couple of weights for each end is 
utn*(\i*i\. Having cut the paper, dampen it slightly with a wet sponge, 
going over it very evenly and working quickly, so that it may be 
artachi'd to the board before quite dry. The damp side must be up. 
Thft Htraight-edge is placed an inch outside of the cutting-off line and 
the weights put on, one at each end. Turn up the edge of the tracing 
pApor, as shown in Fig. 29. and apply the mucilage or paste brush, 
orMilng the edge down firmly with a straight-edged ruler or paper 
I. The opposite side of the tracing paper is treated in the same 
Mnd then the two remaining sides, care being taken to stretch 



the paper carefully by pulling the edge of the paper gently with the 
tips of the fingers, before the weights are put on the straight-edge. 
Any superfluous water may be removed with a blotter. The whole 
operation, as before stated, should be done very quickly, as in a warm 
room the paper soon dries. 

Mounting Paper for Coloring 

Should there be any wash coloring to be done after the tracing is 
made, it is usually done on the back. The tracing is therefore taken 
up, cutting close to the pasted edge, so as to leave as much margin as 
possible for the second mounting. The drawing paper is also taken 
off the board and a clean white sheet, not so large, put in place of it. 
The tracing paper, being turned over, is again mounted to the board 
as previously described, care being taken to get no paste inside the 
cutting-off line, which should have been distinctly marked. While the 

Flff. 29. Mounting Tracing Paper 

paper is drying the colors can be mixed. Allow the coloring to thor- 
oughly dry before cutting off the tracing, which should be done with 
a sharp knife, following the cutting-ofC line very carefully. 

Mounting Cloth for Tracing or Coloring 

The process described above is for paper tracings only. Cloth can 
be mounted in the same way, except that on no account should a damp 
sponge touch it, but it may be stretched without damping it at all, 
though not so satisfactorily. If the tracing cloth is put in a cold 
or slightly damp place over night it can be stretched very nicely, 
using a thin glue instead of paste. When one edge is firmly fixed, the 
other should be pulled very tight and extra weights put on the straight- 
edge to hold It in place while applying the glue brush. Mounting for 
coloring is done the same way, it being, of course, understood that 
the coloring is done only on the dull side of the cloth. Very satisfac- 
tory results can be obtained by not mounting tracing cloth at all, but 
simply using a number of iron tacks driven with a magnetized ham- 
mer, as elsewhere described. 

Mounting Blueprints, Maps, Etc. 

Blueprints, maps, drawings, old tracings, etc., are often mounted on 
linen or cotton to preserve them. The linen or cotton should be cut 
larger by several inches than the blueprint, and a drawing board about 
the same size used. Soak the linen well in water, wringing it out 
between the hands until all the superfluous water is squeezed out. 



when it should be unfolded and shaken out. Lay it across the board 
and commence tacking one edge, beginning at the center and pulling 
gently; place a tack about every two inches along the edge of the 
board, as shown in Fig. 30. The other half of the same edge must 
be done in the same manner. The opposite edge is done next, stretch- 
ing the linen well each time before a tack is driven; commence at the 
middle as before and work toward each end. The two remaining 
edges are done in exactly the same manner, and all is now ready for 
the paste, which should be prepared for use before the linen is 
stretched. The paste can be made either of starch or flour. A suf- 
ficient quantity is mixed in cold water to about the thickness of cream. 
Hot water is then poured over it, gently stirring it meanwhile; the 
whole is then put in a saucepan on the fire and stirred until it begins 
to boil over, when it is lifted from the fire, poured back again into 
the basin, and is ready for use. An apron of some kind is fastened 
around the neck, reaching to the knees, to protect the clothes from 


Pig. SO. Moontiiig Blue-prints and Maps on Linen 

getting soiled. Taking some of the paste in the hand, slap it over the 
board, rubbing it well into the linen with both hands, using more paste 
if required, until the whole surface is covered. Now, commencing at 
the lower edge and at the left-hand end, holding the tips of the fingers 
close together push the superfluous paste along to the center of the 
board as you travel along from left to right. Go to the opposite side 
of the board and do the same thing, forming a ridge of paste along 
the middle of the board, which is scraped off with the hand into the 
basin. With both hands go all over the board again until the paste 
is nicely and evenly spread all over the linen. 

An assistant is now required. The blueprint is dampened on the 
back with a sponge and placed gently in correct position on the linen. 
One-half is to be pasted at a time. The assistant holds it up by the 
two corners at an angle of about 30 degrees, while with a large blotter 
in one hand held to the print you rub gently but firmly over it, the 
assistant letting the print gently yield to the pressure you bring to 
bear upon it. Passing over to the other half, it is lifted from the 
board and then treated in the same way. Wherever an air bubble 
appears it can be pricked with a needle, and the blotting pad placed 
over it, while with a circular sweep of the other hand you press it 
firmly to the board. Should any obstruction unfortunately have been 
left between the print and the linen a slit can be made in the former 
and the obstruction removed when it is again pressed to the board. 


The whole should thoroughly dry before any attempt is made to 
tear it from the board. Often this is not done till the following day. 
Cut through the print and linen with a sharp knife along the cuttlng-off 
line all around the board. Then, lifting the corner, pull gently but 
firmly in a slanting direction. The tacks and trimmings are then 
removed and the board cleared away. The case of a blueprint has 
been taken. Maps, drawings, etc., are done in precisely the same 
manner. Before the print is taken up, a coat or two of clear copal 
yarnish is sometimes applied to preserve it still more. 

Mounting Paper on Drawing Board 

A quick and very satisfactory way of mounting drawing paper to 
the board, instead of using tacks, is resorted to by many draftsmen 
in the following manner: The paper is laid flat on the board, right 
side up. A moderate sized sponge filled with water is wiped all over 
the surface of the paper within an inch or so of the edge all around. 
The superfluous moisture is mopped up with the sponge, and the edges 
therf dampened. One half of the sheet is turned precisely over the 
other half, edge for edge. With a well-filled mucilage brush go quickly 
around the three edges of the upturned half of sheet, and turning it 
over again, press the edges firmly to the board with the thumb or a flat, 
thin stick. Turn the other half of the sheet over the first and proceed 
in the same way. When thoroughly dry, the paper will stretch very 

Still another way of mounting paper is to lay the sheet down wrong 
side up and with a small glue brush dipped in liquid glue go all 
around the edge of the paper at once. Quickly sponge all over the 
surface with plenty of water, keeping clear of the glued edge. Having 
mopped up the superfluous moisture with a dry sponge, turn the paper 
completely over and stretch it to the board by going over the surface 
with the flat of the hand or a clean, dry duster, working from the 
center to the edges, pressing the latter all around firmly to the board 
with the fiat of the thumb or a thin, flat stick or ruler. Either of 
these methods has been successfully used in many offices, especially 
architects*, but for important work the method described under the 
head of "Mounting Tracing Paper." and illustrated in Fig. 29. should 
be resorted to. 



It is evident that the index system suitable for one drawing-room 
may not be exactly what is wanted in another, where a different prod- 
uct of manufacture, and different conditions in general, call for some 
individual modifications. It is therefore necessary to assume, perhaps, 
that the index systems outlined in the following may not be directly 
applicable to a majority of drafting-rooms, but the general principles 
Involved will be, and ought to be, used as guides in devising any 
drawing-room card index system. 

Index System for Drafting'-room with a Great Variety of Work ♦ 

The greatest difficulty in devising a satisfactory index system* is 
met with in shops having to deal with a great variety of work. For 
drafting-rooms in shops where the product is limited to only a few 

Drawing No. A-612 Date March 6 1905 

Drawn by M, C-r Checked by Potter 

Casting Detail : 

Special head for /2 

Brown & Sharpe Milling Machine. 

Piece No. 656 

Remarks: For construction see A-109. 

For milling hexagon nuts. 

PiflT. 31. Index Card for Shop Drawinfir 

Standard machines, or articles, which are turned out in great quanti- 
ties, the problem is a comparatively easy one. But in the case where, 
even if the shop be comparatively small, the accumulation of drawings, 
sketches, patterns, and such tools as the drafting-room is often ex- 
pected to take care of, becomes of a vast scope even in a few years, 
on account of the variety of work, a more detailed system becomes 

The system indicated in the following may, at first glance, seem 
somewhat elaborate, but a little extra expense added in the beginning 
will more than repay itself in the long run. The main factor to be 
taken in consideration when planning a system Is, of course, the 
rapfdlty with which a thing looked for can be found. The somewhat 

* Machinest. September. 1906. 


greater care needed to keep up a complete system will hardly amount ^ 
to anything compared with the time wasted in trying to locate things 
looked for in an incomplete and patched up card index system. 

The words, "drawing," "shop sketch" and "customer's sketch" re- 
ferred to below are defined in this system thus: 

Drawing. — Any tracing or drawing for machines, tools and devices 
manufactured by the firm as a standard article or used in the shop. 

Shop sketch. — ^Any drawing, made in the drawing-room, of special 
tools that are ordered in small quantities by customers. 

Customer's sketch, — Any drawing, tracing, sketch or blueprint thai 
has been sent to the firm by outside parties or customers. 

The drawings are indexed on cards (see Fig. 31) on which is stated: 

1. Number and letter of drawing (the letter indicating the size of f 
the drawing). ^ 

2. When made. 

3. By whom made. 

4. By whom checked. 

5. Omplete title of the drawing. 

6. Piece number (if a casting, this is also the pattern number). 

7. Remarks. 

These cards are numbered, when they are blank, with the drawing v 
numbers in rotation, and are kept in numerical order. As soon as a 
drawing is made, the first blank card is filled out and its number 
stamped on the drawing. The card is then placed in the index, accord- 
ing to the following rules: In the first place, tools and machines 
should be indexed in general classes, and all general attachments for 
the machines should be indexed under the heading of the machine 
with which they are used. For example, cutters of every description 
should be indexed under the word "Cutter," and sub-headings should 
be provided in the index if the number of cutters of different descrip- 
tions make a sub-division necessary. Again, for example, "Dividing 
head for milling machine" should be indexed under "Milling Machine" 
and sub-divisioned under "Head.^' Fig. 32 of an index arranged in 
this manner will make further explanations unnecessary. 

Jigs and fixtures that are to be used for certain operations in 
manufacturing parts of standard machines and tools are indexed in 
the same divisions as the parts on which the operation is to be per- 
formed are indexed under; for example, a fixture for boring head for 
milling machine is indexed under "Head" for "Milling Machine." In 
cases where it is found difficult to decide under which heading to 
place a certain tool or fixture, it is advisable to make out two or 
even more cards under such headings where they are most likely to 
be looked for. The files for the cards should be kept in the most 
accessible place in the drafting-room, where everybody having to use 
them can do so with convenience. 

The drawings are filed in drawers in the drawing-room, out a "record 
blueprint" of each ought to be kept in a fireproof safe or vault; of 
course one must be very particular about replacing these "record blue- 
prints" every tiVne a change is made on the original tracing or drawing. 


Sketches, as a rule, being used only a very limited number of times, 
ought not to be traced, but drawn either In copying Ink or copying 
pencil, and copied In a special copybook used for the purpose. The 
sketch la marked with the page number of the copybook vhere It la 
copied. These sketches could, of course, he indexed on the Index pages 
of the copybook, but when one copybook after another Is filled out It 
would be a waste of time to have to go through the Index of each 

one In order to And what is wanted; therefore a card Index Is provided 
for these sketches also, where the cards are put in order according 
to the names of the customer. 

There Is also an additional card Index for these sketches where 
the cards are put in order, not with reference to name of customer, 
but according to name and kind of tool drawn on sketch. Customer's 
sketches are not listed in any card Index, but are kept In proper order 
In e common letter-file. 

There Is no need of providing for a card index for the patterns, as 



the pattern numbers are always marked, not only on the drawing itself, 
but also on the index card for the drawing in question. However, it 
Is both convenient and necessary in many cases to be able to tell from 
the number of the pattern what machine or tool this pattern applied 
to; therefore a book is provided with pattern numbers in rotation, 
where the patterns are entered as soon as a drawing is made. 
It is not only necessary to keep a good record of drawings or pat- 

No. of copybook 6 Page 314'Date March 12 1905 
Drawn by G. R. Checked by Potter 

Customer's name : American Tool Works Co. , 

Cincinnati, Ohio. 
Tool: Taper Reamer- 
Remarks: For Brass — made to their sketch. 

Fiff. 38. Card In Index Arranged According to Name of Customer 

terns that have been made, but equally as important to have a com- 
plete record of blueprints, sketches, patterns, etc., when in use. All 
blueprints given out from the drawing-room must be charged to the 
person for whose use it is furnished, whether he be some one in 
the shop or an outside party. For this purpose there is a special set 
of cards, one card for each drawing, this card being provided with the 
drawing number; these cards are kept in numerical order. When a 

No of Copybook 6 Page 314 Date March 12 1905 
Drawn by G. R. Checked by Potter 

Tool: Taper Resuner. 

Customer's name: American Tool Works* Co. , 

Cincinnati, Ohio. 
Remarks: For brass — ^made to their sketch. 

Flff. 34. Card In Index Arranir^d According to Class of Tool 

blue-print is given out by the drafting-room, the name of the person 
for whose use the blue-print was given out, is recorded on the card 
with the same number as the drawing. This enables anyone to find ai 
a glance where every blueprint of a certain drawing can be found. 

When sketches are sent out in the shop, it is noted in the copybook 
Itself on corresponding page, to whom and on what date, sketch wag 
given out. As these sketches have to go from one department to 
another, each department foreman is expected to keep a record of 


when and to whom he sent the sketch, when he was through with it. 

When the work is finished, the sketch is returned to the drafting-room 
I and the date when it was returned is noted down in the copybook on 

page number corresponding with sketch. Customer's sketches are 

never sent out in the shop, but are kept as records and for reference 

in the letter-file mentioned above. 
i A system laid out and made up in accordance with the principles 

' above will prove itself very satisfactory, not to say necessary, for the 

j drafting-room in a shop having a great variety of work to do. 

! Card Index in the Jobbingr Shop * 

i The index system of the drafting-room in a general Jobbing and 

I n'Piiir sliop also offers difficulties. The system for such a drafting- 


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Pi fir- 36 

room, as outliii«'d below, has been devised by a man in churge of a 
shop doing a general line of repair work and some building of new 
machinery, in a place ^\here there is little scope to take up any 
standard line of work or even to make the same machine twice with- 
out alteration. To avoid endless confusion, he has found it necessary 
to evolve some system of keeping records of the machines and parts 
of machines sent out. as well as of the drawings, and his experieiue 
undoubtedly will prove useful to others having to work under similar 

In most shops of this kind a part of the work is done to blueprints 
or sketches supplied by the customer, and part to drawings made by 
the firm's own staff; and the patterns are sometimes the customer's 
property and sometimes the firm's. The remainder of the work is 
repairs, overhauling, refitting, etc., of which no record need be kept. 
The problem resolves itself into these requirements: First, to be able 
to find at any time the drawing to which any part of any machine 
was made, given the customer's name. Second, to have a complete 

• Macuineby. June, 1107. 


Index to all patterns, drawings, foreign blueprints, etc., to save duplica- 
tion of any of these where they can be worked in on another order. 

On receipt of an order front a customer it is written out on a 
form, a copy of which goes to the drawing office, pattern shop, boiler 
shop and machine shop, or such of these departments as have work to 
do on that order. 

We will suppose that this order is for a machine to be made to the 
firm's own drawings. The drawing office then, on receipt of this order, 
makes out a production sheet on bond paper forms, giving name and 
number required of each part, drawing number, pattern number if a 
casting, and material of which it is made. This production sheet 
should include everything required, bolts, nuts, oil-cups, gaskets, split 
pins, name-plate and every detail, no matter how small. In the case 


Si. &01 

21 . 



-.» ■.•■ .■P■lO^ 

-VtCWTXC^X- - »©'•» 5-9' - too 



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- ref* \c^ 


Fig. 36 

of forgings, it should give, in addition to drawing number, the length 
and size of bar required to make it. The required number of prints 
should then be made from the production sheet, and the order number, 
name of customer, date issued and number of machines required (the 
production sheet should always be made out for one machine only) 
put on the prints, and not on the original, as this may be used again 
later, on other orders. One print should then be sent to the stores 
department, to order the material from, and one to each of the different 
departments having work to do on that order, the pattern shop having 
to issue the patterns and orders to the foundry department. Also one 
print should be filed away as a record under the order number, prefer- 
ably in an envelope, together with any special specification or other 
matter referring to that order only; these will be kept in numerical 
order and should be stored in a fireproof vault, but in a convenient 
place for reference. The original can now be altered to suit any 
future orders or improvements in design without affecting our record 
of that order. Any alterations to the drawings for subsequent orders 


are also made in such a way that there is a record of the original di- 

Now, to duplicate any part of an old order, we have a card index 
of the production sheet prints that are filed under their order num- 
bers. These cards are indexed alphabetically under the customer's 
name; a copy of the card is shown in Fig. 35. This card is filled out 
for each order for that firm and filed away in the index cabinet. 
Therefore, given the customer's name, we can, by consulting this index, 
find the order number under which his machine was built, and by get- 
ting out the production sheet print for that order number we get the 
drawing numbers we require. 

The columns for size and hand save us the necessity of looking up 
two or three production sheet prints, as, for instance, if we get an 
order for a set of grate bars, same as supplied by us with a 48-inch 


ri*i . ^ 

„. I » I- •« H I I ' I I ' ■ "^ 

ITOI-B ^of*C f=\>VX«.'^ — »'-'V 



\-C . * .- _ . - 5 


' \\\-e ... -- -*»■ . I 

\-c • - - • - ^ 


- «%■ 

I - i 

Flff. 37 

boiler for Brown & Co., we look under Brown for Brown & Co.'s card, 
and then down that card till we come to a 48-inch boiler, which will 
give us the order number, and from the production sheet print for 
that order number we can get the pattern number and number re- 
quired. If we had not the size on the card we might have any num- 
ber of boilers built by us for that firm to look up in the production 
sheet prints before we found the 4S-inch size. 

The Machine Xo. column is used in case a customer sells his ma- 
chine to some one else, the number being stamped on the name-plate 
of the machine. • 

The Drawing No. colunm gives the assembly drawing number, and 
may save time if one wanted only an assembly drawing, but it is 
primarily intended for orders such as stacks, smoke connections, etc.. 
which require only one drawing. No production sheet Is made for 
such orders, a bill of material on the drawing giving all information 


The original production sheets have a card index with alphabetical 
guide cards, and are indexed under the name of the machine, as boiler 
under B. A copy of these cards is shown in Fig. 36. The production 
sheets are numbered in order, as made. The shop drawings are in- 
dexed alphabetically under the name of the part. These drawings are 
numbered and filed consecutively as made, and are given the suffix A or 
B. A is the large size (18 x 24-inch) and B the small size (9 x 12-inch). 
The A and B drawings are numbered and filed independently of each 
other. The cards for indexing these drawings are shown in Fig. 37. 
Each part of a machine is on a separate card, and the cards are re- 
written from time to time to keep the parts on the card in order of 
size, smallest size at top, as other similar parts of different sizes are 
made and interpolated. 

If the order should be to make a machine to the customer's blue- 

o^ mm UkCmmoM ^ 

I ' : 

.i(\cflioii\ Co«\«.co -3-^'^&o'-o* ' re, 

.M^aou ^Quuv- Co«\\.Co -— — «*o'-o* ' Tl 

^fe«L)ALW.TAMRT\t4mf^CH\t«C CO 

— ^'-o'^ ro-O* : 9t- 


- &'-G>'jK8d^*«r ,/ro. 


Fig. 38 

prints, we number these prints consecutively, starting with the num- 
ber after that given to the last blueprint on the previous order, and 
giving it the suffix C or D. as 125-C. The suffix C indicates that the 
patterns shown on that print are our property, and the suffix D indi- 
cates the reverse. These i)rints are folded and put in envelopes bear- 
ing the same number, and are filed away in consecutive order, the C 
and D prints being in separate drawers. The C prints are indexed 
with our own A and B drawings, so that we have on the cards a com- 
plete list of all sizes of patterns or designs we have of that particular 
part. The D prinfs are indexed under the name of the part, the card 
being shown in Fig. o8. The column for print number is for the num- 
ber given the print by the customer, and Name of Firm is the name of 
the customer or owner of the print; these two columns are for pur- 
poses of ready identification. 

The foregoing is only a bare outline of the system, but it will be 
sufficient to show its cheapness and adaptability to the work required 
of it. 



Limitlnsr the Volume of the Card Index * 

While the card index has proven a valuable aid in facilitating the 
drawing-room work, It Is, however, apt to become rather voluminous 
if the business is a growing one, and even though one may add all 
the card index guides possible, dividing the index into classes and sub- 
divisions, there will invariably be some sub-divisions that will contain 
more cards than are convenient to look through every time a drawing 
is to be found. 

For this reason a system based upon a principle of classification, as 
described below, will make the index less voluminous, and at the same 
time permit a saving of time when looking up a drawing. It is the 
usual practice to make one card for each drawing indexed. This is. 
however, not necessary as long as there will always be a certain num- 
ber of drawings of the same kind of tools or articles that can conven- 
iently be listed on the same card. The card depicted In Fig. 39 shows 

Class Milling Machine Fixtures. 

Subdivision. .Fixtures for parts of Multi -spindle Drills. 


No. of 






6 131904 



12 31-1905 



For 4-spindle drill, if 

center- distance. 
For 3-spindle drill, 1| 

center- distance. 
For 4 spindle drill, 2^ 

For 4spindle drill. If 

cen ter-distance. 


Plff. 30. Index Card Adopted to Save Space 

plainly the principle employed in regard to using the index guides, 
having first guides for general classes, and then for sub-divisions. On 
the third line of the card is given the general name of the class of 
articles for which the drawings on this card are made. The remain- 
der of the card can be used for filling out from time to time addi- 
tional drawings belonging to this same general description. It will 
be seen that by means of this system the card Index can be easily 
reduced to a fraction of Its original volume. As the draftsman Is well 
aware, the average life of a drawing Is rather short, and still, as super- 
seded drawings have often to be referred to, It Is well to systematize 
the drawing-room so that the superseded drawings are kept on file 
right with the regular ones, but marked "superseded," and with the 
date the reissue took place. In order to save unnecessary delay In 
looking up a drawing, the date when the drawing was superseded 
should also be marked on the card In the Index. With the exception 
of these remarks, the picture of the card will explain Its purpose, and 
• Machineby, Heptembcr, 1000. 


Its general usefulness. Systems of this character have proved a time- 
saving suggestion to many drawing-rooms that used to work under 
difficulties with rapidly expanding card-index systems. 

Blue-print Record Card * 

A firm whose line of work is such that improvements and changes 
of designs and details are constantly being made, must by necessity 
devise some system of properly keeping track of the blue-prints in the 
factory. In an establishment where there are several hundred prints 
in twenty to twenty-five different departments, it is very necessary that 
there be some good system of keeping in touch with every blue-print, 
in order that the proper ones may be corrected when a change is 

The card shown in Fig. 40 is one used to great advantage by The 
Garford Co., to keep track of all blue-prints issued from the drafting- 

MifVCM* MFT ' CMMTWM CHAKC* rM»«.CCO CwtHuiD .-^in-.ti «riun«CO *C««aR« 

^ . ^ UNMOUNTED -- m *> 

/y ^7 y^ MACHINE f-i^ .-^'.Ji^^T 

VS i^. Zi^, MACHINE /i^*r 

Fig. 40. Blue-print Record Card 

room. Each detail is drawn on a separate standard sheet, and mounted 
on pressboard for the shop. Each department has a complete book 
of blue-prints for each type of machine. When a change is made on 
a drawing, a new blue-print is made to supersede each blue-print in 
the factory. On issuing a blue-print from the drafting-room, a card 
like that in Fig. 40 is filled out. The name of the piece is entered 
in the place marked "Name." Blue-print number and drawer number 
(which is the drawer where the tracing is filed) are placed on with a 
stamp in their proper places. In the column marked "Delivered" the 
date is entered, and the department number placed in the column 
marked "Dep't." Under the heading 'Condition." the mounting and 
kind of the blue-print is noted, either mounted or unmounted, machine. 
drop-forge or pattern drawing. For this, a rubber stamp is used. 
When a change is made in the tracing, by looking on the proper card. 

* Machiitekt. August, 1!H)7. 


It Is readll; aeeii where the blue-prlatB are, and which ones are to be 
changed. In the column "Changed." the date when the new blue- 
print Is delivered and the old one la returned, is noted. If for any 
reason It la not necessary to change tbe blue-print In some depart- 
ments, a check or some other mark Is placed In the apace instead of 
the date, and a similar check or mark placed on the back, and the 
reason noted. If, for instance, the piece is a casting and some drilled 
hole were changed from one-Quarter Inch to three-eightlia inch, it 
would not t>e necessary to change the blue-prtnt In the pattern shop. 
Bach department has its own blue-prints, and they are never delivered 
from one department to another without first going through tbe draw- 
ing-room. When a department is through with the blue-print, it is 
returned to the drawing-room, and the date entered In the column 
marked "Returned." 

Card Index for the Draftaman'B Indlvldu&l Becorda ■ 

While in the up-to-date drafting-room the card index found early 

acceptance, and has become a necessary adjunct for the keeping of 

records of various kinds, there la, however, a place In the drafting 
room for the card Index where It has yet to be more generally adopted, 
and that Is as an Individual adjunct to each draftsman's outfit. Years 
ago Nystrom said: "Every engineer should make his own pockecbook, 
as he proceeds In study and practice, to suit his particulsr business," 
and there is no better way of compiling a pochetbook than by the use 
of the card Index. Outfits for tbe purpose may be purchased In all 
styles and prices, from the trial outfit of 3 x 5 cards, in % pasteboard 
case and costing about 75 cents, up to the most elaborate cases and 
trays for tbe S x 8 cards. 

* Macuinkby, Norcmber, VttOi. 


Pig. 41 la a Bketcta of a very cheap and serviceable index box that 
can be readily put togetfaer In the pattern shop, and Is In some ways 
better suited to this particular purpose than those purchased of the 
regnlar dealers in such goods. Being made of ^-Inch pine, planed 
down to almut % inch, tt is very light and much more easily bandied 
than the regular cases, which are usually made of oak. Another point 
In its favor ts that it can be made much shorter than any of the regu- 
lar trays which come In lengths of from 12 to 14 inches, and are, there- 
fore, of a size that would prove unhandy upon a draftsman's board. A 
package containing 100 Index cards of medium weight measures a 
little less than an Inch In thickness, so that a box 4 or 5 Inches deep 
will hold a sufficient number of cards to cover a long period of the 
average draftsman's experience. The object should be to compress' 

the entire outfit Into size and weight which shall not greatly exceed 
that of an ordinary reference book. 

Cards for these outfits are provided mainly In 3 x 5-. 4 1 6-, and 5x8- 
Inch sizes, but If the Index Is to be put to all ot the uses which are 
mentioned later, the cards should not be less than the 4 x C-lnch size. 
Either of the two larger sizes, It used In a short, light tray, will be 
found fully as convenient to handle as the ordinary Iray for the 
smaller cards when It Is of the usual length and constructed of oak. 
The cards chosen should be of sufficient size to allow ot fairly lengthy 
computations, and tor mounting complete tables and similar data 
clipped from periodicals. If home-made cards are to be used they can 
be easily cut from manila or stlft white drawing paper, and will answer 
the purpose very satisfactorily. Guide cards are cut from the same 
material and labeled to suit the matter to be Indexed. In the case 
Illustrated no provision whatever Is made for locking the cards In, as 
none Is considered necessary. When It Is desired to refer constantly 
to a certain card or cards they may be easily sllpp<>d out and placed 



on tlie drawing board for the time being, and anj device which makes 
It necessary to lock and unlock in order to do this, or to remove and 
add cards, will, after a short trial, be found to be more of an objection 
than an advantage. 

The usee to which the Index can be put will susgest themselves to 
each draftsman as the reQuirements ol his work present them. In the 
first place there are certain tables to which every draftsman must con- 
stantly refer, and these should form a foundation ol the Index sys- 
tem. Such data as decimal equivalents, squares and cubes, trigo- 
nometrical functions, etc., furnleh the moat natural beginning. These 
are to be found in the b&cdbooka In common use, such as Kent and 
Nystrom, but when only one table Is needed for a particular use, the 
'convenience of drawing out a single card over the necessity of hand- 
ling the whole hook, will at once be apparent. Often several tables 

are used at the same time, and then the pages of the book must be 
turned back and forth, or, perhaps, two or more books must be referred 
to. With the index syetem any number of cards may be placed side 
by side where the draftsman may refer to tbem without trouble. 
Having started with the tables most commonly used the Index will 
grow with considerable rapidity. IF any unfamiliar table or data Is to 
he consulted, much time may be lost In searching for It through the 
different handbooks, but If. when found, it Is copied on to an index 
card, It is then ready tor immediate use If again needed. Clippings 
from periodicals have before been referred to, and the value of a year's 
subscription to any good technical publication will be wonderfully in- 
creased if all of the data that Is published pertaining to one's par- 
ticular line of work Is placed upon the cards. Fig. 42 is an lllustrs* 
tlon of a data card upon which Is mounted one of the tables taken 
from a Mackikert data sheet 
Reviews of all technical books that the owner reads should And a 


material and to perform similar duty. If similar comparisons be made 
of castings and forgings of various kinds, we soon accumulate a quan- 
tity of very reliable information that applies more closely to our par- 
ticular cases than any published data which must, at best, be only 
general in its nature. 

Photographs of machines built, and data connected with them, will 
prove valuable additions to the index. Fig. 44 shows a record of a 
special vertical milling machine, and explains just which parts were 
special and which regular, and provides a complete record of the draw- 
ings used and any information that would be of aid to the draftsman 
if called upon to design a similar machine at some future time. 








Third Edition 


Elementary Principles of Drill Jigs, by E. R. Markham 3 

Drilling Jig Plates, by J. R. Gordon ... - 21 

Examples of Drill Jigs 27 

Dimensions of Standard Jig Bushings - - - - 50 

Using Jigs to Best Advantage, by B. P. Fortin and J. F. 

MmRIELEES - - - 53 

Gopyriffht, 1913, The Industrial Press. Publishers of BIachinery. 
49-66 Lafayette Street. New York City 

4 No. 3— DRILL JIGS 

fittini: and assembling, those parts which are exactly alike require a 
minimum amount of labor when putting in place. This, perhaps, one 
may, without danger of exaggeration, say is in most cases in the ma- 
chine building business the chief consideration. 

In the third place, accuracy is often attained only by the use of 
jigs. There are certain classes of work which could not be finished 
at all within the limits of accuracy demanded, if jigs of some sort 
were not used. 

. It will therefore be seen that the determination of whether a jig 
shall be made may rest upon a number of questions which often de- 
mand great care and practical experience to solve in the way best 
meeting the requirements of the case. 

Drill Jiers 

Drill jigs are used for drilling holes which must be accurately 
located, both in relation to each other and to certain working surfaces 
and points; the location of the holes is governed by holes in the Jig 
through which the drill passes. The drill must fit the hole in the 
jig to Insure accuracy of location. When the jig is to "be used in 
drilling many holes, the steel around the holes is hardened to prevent 
wear. If extreme accuracy is essential, or if the jig is to be used as 
a permanent equipment, bushings, made of steel and hardened, are 
used to guide the drills. 

General Considerations In Designing Jigs 

The design of a jig should depend altogether on the character of 
the work to be done, the number of pieces to be drilled, and the degree 
of accuracy ncessary in order that pieces drilled may answer the pur- 
pose for which they are intended. When jigs are to be turned over 
and moved around on the drill press table they should be designed 
to insure case and comfort to the operator when handling, and should 
be made as light as is consistent with the strength and stiffness 
necessary. Yet, we should never attempt to save a few ounces of 
iron, and thereby render the jig unfit for the purpose we intend to 
use it for. The designer should see that the jig is planned so that 
work may be easily and quickly placed in and taken out, and that it 
can be easily and accurately located in order to prevent eventual mis- 
takes. As it is necessary to fasten work in the jig in order that it 
may maintain its correct position, fastening devices are used; these 
should allow rapid manipulation, and yet hold the work securely to 
prevent a change of location. Yet, while it is necessary to hold work 
securely, we should not use fastening devices which spring the work, 
or the holes will be not only improperly located, but they will not be 
true with the working surfaces or with each other. When finishing 
the surfaces of drill jigs and similar devices used in machine shops, 
the character of the finish depends entirely on the custom in the shop, 
for while in some shops it is customary to finish these tools very 
nicely, removing every scratch, and producing highly finished surfaces, 
in other shops it is not required, neither is it allowed, as it is con- 
sidered a waste of time and an unnecessary item of cost. 


is he who so far as possible eliminates the small items of expense, 
knowing that many small items of expense amount to a large item 
in the aggregate. Not only is the operation of burring expensive, but 
as the class of help usually employed to do this work is unskilled, sur- 
faces are many times left in a condition anything but satisfactory. 
As a consequence, the surfaces of jigs, milling machine fixtures, etc., 
are many times cut away to receive these burrs, thus doing away 
with the necessity of burring, as it many, times happens that subse- 
quent operations remove the burrs. In Fig. 1 is shown a pieoe of work 
having a burr thrown up at a, while Fig. 2 represents a surface cut 
away to receive the burr. 

Factors Determining the Advisability of Using Jigs 

When we wi^h to drill two holes a given distance apart, the location 
of the holes is obtained by means of a pair of dividers set to a scale. 
The location is obtained and prick punched, after which the holes are 
drilled. This method answers nicely when one piece is to be drilled, 
and precise measurements need not be observed. If it is necessary to 


Flffs. 1 and 2. Work with Burr, and Grooved Part of Jiff to Oorrespond 

drill ten thousand pieces, then this becomes a costly method, and the 
work can be done more cheaply if a Jig is made to hold the pieces. 
The jig must, of course, have holes the size of the drill, which are 
properly located. By the use of the jig, the cost of drilling is but a 
fraction of what It would be If the holes were located by dividers, and 
the surface prick punched as described. As we fiave already said, the 
first factor which must be considered is the cost of the jig. If the cost 
of the jig, plus the cost of drilling, would exceed the cost if the pieces 
were first prick punched and drilled as formerly described, then the 
making of the jig would not be considered unless a greater degree of 
accuracy was necessary than would be liable to be the result of the 
method mentioned. When a jig is to become a permanent part of the 
equipment of a shop, its first cost is not so much a matter of considera- 
tion as when only a limited number of pieces are to be drilled. Yet 
no unnecessary expense should ever be allowed. 

Means for Locating Work in Jigs 

Many times when only two pieces are to be drilled which must be 
exactly alike as regardo location of holes, it is cheaper to make a 



more holes are drilled, and before all are drilled, it would cause a 
variation that would in all probability spoil the piece of work. When 
but a few pieces are to be drilled with a Jig it is not generally con- 
sidered advisable to make Jigs with fastening devices, the won. being 
held in place with a clamp, as shown in Fig. 7. In order to do away 
with any possibility of change of location, a pin is forced through 
the Jig hole and the hole in the work after drilling the first hole. If 
many holes are to be drilled in a piece tt is advisable to have two 
pins. After drilling a hole in one end of the piece, force in a pin; 
then drill a hole in the opposite end. and place a pin in this hole, as 
shown in Fig. 8. The pins in opposite ends of the piece will prevent 
ii:s slipping when the rest of the holes are drilled. Many different 
f6rms of fastening devices are provided, the design depending on the 
class of work. One of the most positive methods consists of a screw 
which passes through a stud or some elevation on the Jig, and presses 






I, ^\ 












Fig. 7 

Fig. QMmtkiimrpfN.r. 
FlgB. 7 and 8. Means for Holding* Work In Drill Jiff a 

against the work, forcing it against the locating points, or stops, 
they are called. The screw may have a knurled head, as shown in 
Fig. 9, or a thumb-screw may be used, Fig. 10. Sometimes it is neces- 
sary to exert greater pressure than can be applied by means of a screw 
of the ordinary form. Then, it is possible to make a screw with a 
round head, drill a hole through it, and through this hole pass a piece 
of wire as. shown in Fig.-ll. By this screw, sufficient pressure can be 
applied. When it is necessary to exert a greater amount of power 
than would be possible by the use of a pin of the length shown in 
Fig. 11, one may be used that will slide freely in a hole in the head 
of the screw. A ball placed pn each end prevents its falling out. By 
getting the full length of the pin on one side of the screw-head, as 
fesiiown in Fig. 12, a much greater amount of power is obtained. At 
times the stud which supports the screw may interfere with the plao- 



ence to a screw when possible, but at times the piece of work may 
be subjected to repeated Jars which would tend to turn Si cam, thus 
loosening the work. In such cases a screw is preferable. If a cam 
would be in the way when putting in or taking out work, it may be 
made remoyable, as shown in Fig. 15. At times a tapered piece of 
steel in the form of a wedge may be used to hold work, as shown m 
Fig. 16. 

Simple Forms of Drill Jigs 

When many pieces are to be drilled in a Jig made in the simple form 
shown in Fig. 17, the drill wears the walls of the holes, enlarging 

n^. IS. CUunp Screw Mounted In Removable Stud 

them sufficiently to render accuracy out of the question. Where Jigs 
are to be used enough to cause this condition, the stock around the 
walls of the hole may be hardened, if the Jig is made from a steel 
that will harden. If made from machinery steel, the stock may be 
case-hardened sufficiently to drill a large number of pieces without the 



F ig . 1 5 J^u^J^'w^v^v. F. 

Fiffs. 14 and 16. Eccentric Olamp fbr Simple Drill Jlg» 

walls wearing appreciably. This, however, would not answer when 
accuracy is essential, as the process of hardening would have a tend- 
ency to change the location of the holes. 

Guide Bushings 

When the Jig is to be used for permanent equipment, or where many 
holes are to be drilled, it is customary to provide bushings — guides — 
made of tool steel and hardened. These are ground to size after hard- 
ening, and being concentric, may be replaced, when worn, by new ones 
of the proper size. It is the common practice to make bushings for 
drill Jigs on the same general lines as shown in Fig. 18. the upper 
end being rounded to allow the drill to enter the hole readily. A head 
is provided, resting on the surface of the Jig; the portion that enters 
the hole in the jig is straight, and is ground to a size that insures 
its remaining securely in place when in use. 

If the hole is sufficiently large to admit a grinding wheel, it is 



ground to size after hardening. In such cases it is, of course, neces- 
sary to leave the hole a trifle small — 0.004 inch — until it is ground. 
If the hole is not large enough to allow of grinding, or if there is 
no means at hand for internal grinding, the hole may he lapped to 
size by means of a copper lap. using emery ol* other abrasive material, 
mixed with oil. When the hole is to be lapped rather than ground. 

JVae*«iMr|r, It. Y. 
Fig. 16. Wedge Acting as Clamp In DriU Jig 

leave a smaller amount of stock to be removed by the operation, say 
0.001 inch or 0.0015 inch. After grinding or lapping the hole to size, 
place the bushing on a mandrel and grind the outside until it is a 
pressing fit in the hole. While on the mandrel, be sure to grind the 


Pig. 17. Simple Form of Drill Jig without Bushings 

under portion of the head, a. Fig. 18, to Insure its being true with the 
body. Before starting to grind the outside of the bushing, test the 
mandrel for truth. This should be done alter placing the bushing on 
it rather than before. 

It ia the custom in a few shops to make the outer portion of bush- 
Inga tiq^red, as shown in Fig. 19. Unless there is a suflicient reason 
for 10 doing, this is to be avoided, as the operation of making a tapered 



hole, unless it is bored on the taper with an inside turning tool, is not 
likely to produce a hole, the axis of which is at the desired angle to 
the surface of the jig. The outer portion of the bushing can easily be 
ground to the desired taper, but there is the liability of a particle 

Fig. 18 

Fig. 19 
Flflr*. 18 and 19. Bushings tor DriU Jigs 

of dust getting in the hole when placing the bushing in the jig. A 
tapered bushing, in order to get the proper taper, necessarily costs 
a great deal more than a straight one, and cannot answer the purposa 
any better, and probably not as well. 

Types of Drill Jigs 

The shape and style of the jig must depend on the character of the 
work, the number of pieces to be drilled, and the degree of accuracy 
essential. It may be that a simple slab jig of the design shown in 
Fig. 20 will answer the purpose; if so, it would be folly to make a 
more expensive tool. If we are to drill a piece of work of the design 
shown to the left in Fig. 21, and but one hole is to be drilled in each 
piece, then a jig made in the form of an angle iron, as shown to the 
















Fig. 20. Slab Jig of Simplest Design 

right in Fig. 21, works nicely, and is cheaply made. As it is not neces- 
sary to move the jig around on the drill press table It may, after 
locating exactly, be securely fastened to the table. In designing such 
a jig, it is advisable, when possible, to have the work on the side 



as few shops carry such steel in stock, crucible tool steel is generally 
used. The ends of the legs should be ground true with the seating 
surface — that is, where the work rests— of the Jig. To accomplish this 
a surface grinder should be used. As the operation of grinding leaves 
a number of projections on the surface ground, and as these ridges 
or projections would wear away as the legs were moved back and forth 





riEce OF ruottK 

Fig. 32. Jig with Pivoted Leaf 

on the drill press table, it is advisable to remove them by lapping on a 
flat lap, thus producing a perfectly smooth, true surface. In this way 
we reduce the wear to a minimum. 

For certain classes of jigs the legs may be short, not more than 
Vj inch long; but for jigs of the style shown in Fig. 22, where the 
tool is held fn the hand, it is necessary to make the legs longer to 




Pig. as. Part of Jig with Pivoted L^af, Showing Method of Holding Round Work 

keep the fingers from coming in contact with the chips on the drill 
press table. The legs should be located so as to do away w^ith any 
tendency of the jig to tip up when the work is being drilled. 

Relation Between Accuracy of Jigs and Accuracy of Machines on 

which They are Used 

While it is necessary to observe extreme care in designing drill Jigs 
to prevent any tendency of the jig to tip, and to have the legs ground 
and lapped on a true plane, it is just as necessary that the drill 
press table should be perfectly at right angles to the spindle, and that 
it should be true and flat. Otherwise, the holes will not be at the 
desired angle with the working surface of the work. 

In shops where interchangeable work is produced, or where the 
work must in all respects be machined correctly, the condition of the 
various machines is closely watched, and especially such parts of the 
machines as affect the accuracy of the finished product. Drill press 
tables arc planed over when out of true, or are lined up to insure their 
being at right angles to the spindles of the drill press. This may be 
done by placing a bent wire in the drill chuck, the wire being bent 
so that it will describe as large a circle as possible, and yet be free 
to swing. The end of the wire is bent so that the point will come in 


\o. 3— DRILL JIGS 

blow holes in castings, a reamer is liable to alter its course and to 
change the location of the hole. While for many purposes this Blight 
alteration of location might be of no account, yet for work where accu- 
racy is essential, it is out of the question. 

After drilling and boring the first hole, the Jig may be moved on 
the face-plate, and the other holes produced. It is abvious that In 
order to produce holes that will be at right angles to the base of the 
jig, the face-plate of the lathe must run true, and should be tested 
each time it is used for any work where accuracy must be observed. 

Method of Locating Holes When Accuracy is not Essential 

Where there is no model, and it is not considered advisable to make 
working models of the various parts, the location of the bushing holes 
may be obtained by laying out the various points on the jigs. In such 
cases a drawing is usually furnished, and the dimensions on same are 
transferred to the face of the Jig. If it is not necessary to have the 
holes exact as to measurements, the laying out may be done with a 
surface gage, the point of the neodio being set to a scale. The scale 

Mtirhintr^, If. Y. 

T\tc. 26. Angle Iron -with Oroove for Scale 

may be clamped against an angle iron, as shown in Fig. 24. or an angle 
iron may have a groove of the width of the scale cut across Its face 
at right angles to the base, as shown in Fig. 23. The scale should be 
a cood fit in the groove, so fitted that it will stay securely at any 
point from frictional contact with the sides of the slot, or a spring may 
be so arranged as to insure the proper tension. 

Mothod Asauring a Fair Degree of Accuracy 

Where greater accuracy is essential, the working points should be 
obtained by means of a height gage, as shown in Fig. 26. By means 
of such a tool the measurements may be fairly accurate, as the vernier 
scale allows of readings to one-thousandth inch. When the lines have 
been scribed at the proper locations they are prick punched. In order 
to prick punch exactly at the intersection of lines the operator must 
wear a powerful eye-glass, and use a carefully pointed punch, ground 
to an angle of GO degrees. If the punch marks are made very light at 
first, the exact location may be observed nicely. The punch marks 
should not be deep, as there is a liability of alteration of location If 
the punch is struck with heavy blows. After the various points have 
been located and punched, the Jig may be clamped to the face-plate 
of the lathe, and the bushing holes carefully drilled and bored to size. 



the face of the jig with the punch mafk as center. This enables us to 
approximately locate the button. If the hole to be produced has its 
center 2 inches from the base a and 4 inches from vertical side h. 
Fig. 29» we would locate the button — provided it was ^ inch diameter — 
1% inches from a, and Z% inches from h. This can be done accurately 
by the use of a vernier caliper, or we can lay the jig on the side h, and 
by means of a length gage, or a piece of wire filed to the right length, 
accurately determine the distance from h to the button. The jig is 
then placed on the base a and the other dimension obtained in the 
same manner. The buttons may be located more easily by the use of 
a vernier height gage, if one Is at hand. 

If there are to be several bushings on the face of a jig, a button 
may be accurately located where each hole is to be. The jig may be 
clamped to the face-plate of the lathe so that one button is located to 
run exactly true. This is done by means of a lathe indicator. When 

MatMm»rp, A. K. 

Flfir- 27. Cored Holes with Inserted Brass Pieces fbr Centers 

the jig has been so located that the button runs perfectly true, the 
button may be removed and the hole enlarged by means of a drill, so 
that a boring tool can be used to bore it to the proper diameter. 

Locating the Holes on the Milling Machine 

In some shops it is not considered advisable to locate a button at 
the desired position of each bushing hole. One button is located and 
the jig is fastened to the table of a milling machine having a corrected 
screw for each adjustment. Then, after one hole is accurately located 
and bored, it is a comparatively easy matter, by means of the graduated 
dials, to obtain the other locations; however, this method should never 
be used unless the machine has all its movements governed by "cor- 
rected" screws, as the screws ordinarily sent out on milling machines 
are not correct as to pitch, and if used, serious defects in measurements 
will result. Many tool-makers, therefore, prefer using a vernier scale 
and vernier attached to the knee and table of the milling machine, 
for accurate work, as they are then independent of the inaccuracies 
that may be present in the feed-screw. 



Fig. 30 shows a Jig clamped to an angle iron on the table of the 
milling machine. The angle iron is located exactly in line with the 
travel of the table, and the Jig fastened to it. The button D, which has 
previously been accurately located, serves as a starting point, and the 
Jig must be located so that the button is exactly in line with the 
spindle of the machine. This is accomplished by moving the table 

/ — . 

\ / 


/ / 


JVAffAswtf^irt ^••% 

Fig. 28. Buttons tor Looatlnff Hol«s In Jigs 

until the sleeve A on the arbor B will just slide over the button D. 
The hole in A must be a nice sliding fit on the arbor B and also on 
the button D, In order to insure accuracy, the arbor B must be turned 
to size in the spindle just as it is to be used; or, if a portable grinder 
is at hand, the arbor may be fitted to the spindle hole or to the collet, 
as the case may be; the portion which receives the sleeve A may be 



Mmekknarw, S.T» 

Fig. 29. Loc&ting a Hole by Me&ns of & Button 

left a trifle large, and may ho ground to size in place on the machine. 
The portable grinder is located on the table of the machine. 

After the Jig has been accurately located so that the button 7) allows 
the sleeve A to slide over it. the arbor B may be removed from the 
spindle, and a drill be employed to increase the size of the tapped screw 
hole that received the screw used in fastening the button. Best results 
follow If a straight-fluted drill, as shown in Fig. 31. is used. The drill 
ahould not project from the chuck or collet any further than necessary. 



thus Insuring the groateflt rigidity possible. After drilling, a boring 
tool of the form shown in Fig. 32 may be substituted for the drill, and 
the hole bored to siie. The machine ma; now be morcd to position 
for the next bushing hole by obBerTfng the dimenslonB given. The 
operator should bear In mind that the Bcren used In getting the spao- 

Flff. 30, LookOSE BoUa la Uia MWlnv Hubliia 

Ings must be turned in the same direction at all times, otherwise tha 
backlash will render accuracy out of the question. 

While the foregoing relates to plain Jigs, the same principles apply 
to those of more complicated design. In the next chapter attention 

FlvH.3] Knd 3fl. Qtr&lffbt.Fluud I>rUL mnA Iii«*rt«<l OutUr Bortllf TOOl 

Is given to a different and original method of locating the holes 
in jigs, using the drill press for this work exHualvely, and Chapter III 
Is devoted to examples of actual designa of drill Jigs, showing how 
the elementary principles outlined above are employed in the practice 
of the machine shop. 



Resting the 6^4 gage on the table, and with one end touching tilt 
plug, the parallel piece, C, Fig. 34, is brought to Juat touch the other 
end of the gage and is then clamped to the table. This la not T017 
difficult if one end of the parallel is left free and the other end 
is clamped tight enough to permit the free end to move somewhat 
stiffly. After locating and clamping the parallel, C, the other parallel 



Tig. 33. Drill PreHH arranfred for Drilllnf? Jlgr Plates 

is clamped in position, but it must be placed square with the first 
parallel. This is more difficult than in the first case, but is not at all 
difficult If one man can be employed to clamp the piece while another 
holds the square and gage. The reason for making the gages 6i^ and 
8% inches long instead of 5% and 7Ts inches, respectively, is that it is 
not desirable to have the edges of the plate touch against the parallels, 
as chips could get between the two and destroy the accuracy of the 
measurements; allow the gage to be V4 inch longer than the distance 



required, and fill in the space with ^ inch diameter gages, as shown 
in Fig. 34. 

For gages over 1 inch in length use flat brass rods or strips about 
% inch wide and % inch thick, and cut them a little longer than the 

ikJmunat /^«m. A. r. 

Flff. 34. Plate in Position tor Drilling First Hole 

finished length. One end is finished square and the other end is 
rounded as shown in Fig. 35. In making the gage, if too much metal 
is removed, it is an easy matter to pene the stock out to make up 
for any reasonable error. The length of the gage is stamped on it, and 
when the operation is completed it is put away for future use. 
Having located the parallels, the plug is removed from the bracket 



Jn4uttr1ml Pmm. tf.r. 
Flff. 36. T]rp« of 0*ffe used when Drilllnar Jiff Plates 

and the bushing replaced. The drill should, of course, fit as snugly 
to the hole in the bushing as it can and run without cutting. The 
bushing should support the drill to within a distance equal to the 
diameter of the drill from the plate to be drilled, and care should be 
taken not to drill through the plate until all the holes have been 
■tarted. After drilling the first hole, to place the plate for the second 
hole, distant 2 inches from the first, it is moved along the parallel, C, 



and a gage 2^ Inches long placed as shown in Fig. 36, and when so 
placed is ready for drilling. The third hole requires three new gages, 
since it is 1 inch off the line of the other two holes, as shown in Fig. 37. 
For holes which are to be finished 3/16 inch to % inch in diameter, 
use first a small drill, size No. 52 to No. 30. After the holes are all 
drilled to this size, then enlarge them, by the use of a series of four 
lip counterbores, to the required size. Where extreme accuracy is 
required, in the place of the counterbore, a small boring bar may be 
substituted and the holes bored to the size desired. One disadvantage 
of using a boring tool is that it requires a hole in the table equal to 
the largest hole to be bored out, or that the plate shall be kept clear 
of the table by blocking up with parallel strips under it. 

Induttiinl J'rm**, A. K 

FXg. Se. Plate in Position for Diillinflr Second Hole 

Fig. 38 shows a fori a of boring tool which will be found very con- 
venient for use on this kind of work. It consists of the shank. A, 
which is fitted to the taper hole in the spindle, and a split holder. B, 
v.'hich is pivoted to the shank at C. and is locked to it at D. the screw 
at D serving to clamp the boring tool, E. at one end. while F clamps 
it at the other end. Adjustment is obtained by swinging the holder, 
the radial slot, O, allowing it to have quite a range, and the top screw, 
IT, permitting fine adjustment. Split bushings In the holder will allow 
the use of boring tools of smaller diameter if desired. 



portion of the screw Is used to do most of the work of driving the 
table. In the second place, Mr. Grordon claims that his method is 
quicker, the supposition being that the necessary appliances, such as 
parallels, brackets, bushings, etc., are made and ready for use; and 
finally, that there is a very small chance for errors, provided that 
the gages used are marked distinctly. 

These assertions, however, called forth considerable comment in the 
columns of Machinebt. Mr. Frank E. Shailor, in particular, took issue 
with Mr. Gordon on account of these assertions and claimed that there 
were considerable chances for errors. Mr Gordon, however, defended 

Flir* 38. Borlnff Tool 

his method, pointing out that most of Mr. Shailor's objections were 
of little consequence, provided proper precautions were taken. Other 
contributors added their word to the discussion, some siding with Mr. 
Gordon, and some admitting that the methods used both by Mr. Gordon 
and Mr. Shailor would, under proper circumstances, be correct to use. 
It is not possible in this treatise to give place to what was more a 
personal controversy, than of direct bearing upon the subject of drill 
Jig design, it may, however, be proper to mention that the discus* 
sions on this subject appeared in the July, August, September and 
November, 1904, and the January and February, 1905. issues of 



V-block, in which the work rests, and a cover of the simplest design, 
containing the guide bushing. Sometimes, however, they are made 
more universal; the cuts Figs. 39 and 40 show two such designs. 

The Jig in Fig. 39 is intended for drilling pin holes in comparatively 
short studs, and will handle a variety of such work with great rapidity. 
The drill bushing A can be removed and bushings with different size 
holes inserted. The bushing holder B can be raised or lowered to suit 
different diameters of work. The V-block C is fixed, while block D is 
adjustable by means of the screw E for different lengths of studs. Dy 
fastening a strap to the device by screw F, and providing this strap 
with an adjustable screw in line with the V's, studs can be gaged from 
the end instead of from the shoulder, which, when used for gaging, 
rests against the sides of either of the V-blocks. The manner in 
which this Jig is used lends itself well to a variety of work of all 

■n "^^ 





Induct riv I Pr$M, It.T. 
Plff. 40. Jiff for Drilling Holes in Shafts 

This Jig is a simple, yet eflacient and characteristic, example of the 
adjustable type of Jig. It will be noticed that the design does not 
provide for any clamping device for the work to be drilled; this is on 
account of that in this case the holes to be drilled are so small, com- 
pared with the diameter of the shaft or stud, that the stud will stay 
in place by its own weight, or by pressure of the hand on its upper 
aide, the V-groove aiding materially in keeping the work in position. 

The device shown in Fig. 40 is another example of an adjustable Jig 
for this class of drilling. This tool has proved to be of the greatest 
<;onvenience for drilling shafts, spindles or other round pieces. The 
base A is dovetailed and fitted with a lead-screw, which moves the 
slide B in and out. Upon this slide is mounted the adjustable V-block 
C, which can be tipped at any desired angle for oblique drilling, or -set 
perpendicularly to hold the shafts in position for end drilling. The 
adjustable stud D is placed under the outer end of the block to hold it 
firmly in any set position. The arm E is adjustable up and down, for 
<iifferent sized shafts, and is supplied with a complete set of bushings 
for use with drills of different diameters. When mortising bars, in- 
tended to be used as holders for facers, boring cutters, counterbores 

• I»aul W. Abbott, August, 1007. 


to one ilde about th« hand screw O. When the collar has been put In 
place the claxcp U swung back, and In doing bo. Its motion la limited 
by the pin F, which brings it to a stop directly over the collar. At 
the top of the ]lg le a bushing B through which the drill Is guided. 
"When the outside diameter of the collars la Ulcel; to vary, the pins 
D. D, D, may be replaced by a central pin, L, as shown In the separate 
Tlew In the cut, and the collar held on this while ft is being drilled,* 

The Jig shown in Fig. 43 is designed for drllUiig the holes In the 
center of collars, and the method of drilling, described below, also sug- 
gests the value of systematizing the work In using Jlge. The collars 
to be drilled are made of annealed tool ste«l In sizes varying in.thlck- 
nesB as well as in diameter and size of hole, and are cut off from the 

FlB. 4a. JIH ft 

bar on the cold saw. There being a tbree-spludle gang drill In the 
shop, which was 'Idle part of the time, It was decided to make use of 
it in the production of these collars. Four jigs like the one shown in 
the cut were made. They were made to take any diameter or thickness 
of collars within their range. The body of the Jig is a square block of 
steel, with the hole to receive the collars exactly in the center. The 
lower end is threaded left'hand to receive the piece B, which has a 
square hole In the center to receive the wrench C. The ring D Is 
bored taper, and fits the collar operated upon at the top end only, so 
that the collars will drop out ot the Jig easily. DlfTereDt rings "are 
made to fit collars of dtfTerest diameters, and are Just an easy drive 
fit in A, the body of the Jig. They are driven out with a soft punch 
through hole E in piece A. Drill bushings F are also Interchangeable. 
Piece O is a distance piece used when drilling thin collars In order to 
avoid screwing piece B into the jig too tar. It is apparent from the 
cut that these pieces are made to fit the collar at one end, and beveled 
at the other to center In piece B. The reason piece B Is threaded 
left-hand Is as follows: If the collar operated upon should turn In 
■ C, tl. Rowe, January, 1903. 



tern of using the jigs makes this objection of less consequence, as the 
operator has plenty of time to attend to one jig while the collars in 
the others are being drilled. 

Flange Drilling Jigs 

Two examples of flange drill jigs are given in Figs. 44 and 46. The 
jig in Fig. 44 is of the simplest form for this kind'of work, being 
merely a templet, while Fig. 45 shows the appearance and application 
of a more universal device, provided with an indexing plate. In 
cases where flanges and flttings are to be interchangeable,- or to be 
duplicated at different times, the only accurate method of drilling such 
flttings is. of course, by means of a jig or templet which prevents any 
error arising when such parts are duplicated. 

C Loom 

^\^ LOOM 
l»l ■ /Knur 


Section x-y 

JTseMlwry 2f.r. 
Fiff. 44. Templet JI9 for DrlUlng* Flanges 

The templet, Fig. 44, combines simplicity and cheapness. The ring 
proper may be made from a companion flange, the size for which the 
templet is to be used, by cutting off the head and flnishing all over, the 
thickness being approximately one inch. Diameter B is made equal to 
the outside diameter of the flange, and A is the diameter of the bolt cir- 
cle. A removable bushing, such as shown in section x-y^ is used and 
moved from hole to hole as required. The advantage of this loose bush- 
ing over a stationary one in each hole is obvious, lessening the cost of 
the templet more than one-half. The bushing is made from machine 
steel, knurled where indicated, and hardened. The small pin prevents 
the bushing from revolving in its hole with the drill. In such cases 
where a drilling job calls for the same number of bolts in the same 
bolt circle, but different sizes of bolts, all that is necessary Is to have 
twa bushings, with the same diameter E, while C is made to corres- 
pond with the diameter of holes required.* 

In Fig. 45 an adjustable type of jig and the work for which it is 
used are shown. As the number of holes in the work to be drilled. 

• ralvln B. Ross, May, 1900 



many cpenittoiiB In the itiop, however, permit of bo wide a limit of 
erior that fairly accurate jigs can be designed which, having a certain 
degree of flexibility, will accommodate a variety of work. These Jlga 
are valuable In a double measure. In the flrst place they save a great 
deal of outlay for Individual ]lga, and, secondly, many a little Job, 
for which no Individual Jig would be warranted, may be drilled In an 
adjustable ]lg at a great saving of time and gain In accuracy. 

The ]fg shown In Pig. 46, In use in the W. F. t John Barnes shops, 
Rockford, III., la designed with the purpose of securing adjustability, 
so as to adapt the jig to pieces of different shapes and dimensions. The 
base piece A supports an upright F, to which the knee, E, ia bolted. 
This knee holds the drill bushing and Is tongued and grooved to the 




r\a- 40. AdJu'Mtal* Drill lit 

upright BO that It may be raised or lowered for work of different 
heights. The work is held by two slides, B and C. and a. set-screw D. 
The lower slide, C, has a tongue flttlng in a groove in the base, and 
one end ia V-ehaped to give support to the lower end of the work, 
against which It Is made to bear. The slide B has a tongue flttlng 
In a groove In the top of the lower slide, and may thus be adjusted in- 
deiiendently of the latter. 

An adjustable Jig also provided with an Indexing feature, Is shown 
in Fig. 47. This Jig Is Intended for drilling the clearance holes In 
Email threading dies. As these holes are located on different distances 
tram the center according to the diameter of the thread the die is In- 
tended to cut. one Jig would be necessary for <'ach diameter of thread 
In the die. although the outside dimensions of the die blanks are the 
same for wide ranges of diameters of thread. To overcome the necea- 
slty of BO many individual Jigs, an adjustable strap or slide C Is pro- 



extends over the top of the work and clamps down upon it, It holds 
the work securely in place. The clamp is bolted to the plate by the 
screw h, and the work is clamped by screw g at the other end. Four 

I I 

I I 


Induttrtml Prtu, S.Y. 

Fig. 48. Piece to be Drilled in Jiff, Tig. 40, and Detail of Olamp and Feet 

legs c support the body plate A, and raise it up high enough so that 
the work clears the table when the Jig is placed in position for drilU 
Ing. The oblong hole in the plate C permits the clamp to be moved 
back far enough to get the work in and out of the Jig. 


JnUtutrUU. J'nM, S. T. 

Tiff. 40. Jiff fbr DrlUinff Piece Shown <n Flff . 48, with Work in Position 

Large size plates, all planed up, may be kept in stock for the Jig 
bodies so that pieces of the required size can be readily cut off when 



C la forced into the Jig; trom tbe Inside until the slioulder bears ftrmlr 
kgalDflt the upper arm of the ]lg. Thie combined bushing and guide la 
made In a single piece, instead of Inserting drill bushings and a guide 
piece separatelj, because the variation allowed for the holes la greater 
than any that la likely to be incurred In the hardening of the bushing. 
Fitted tightly in tbe hole in the base of the Jig la tbe aleeve. D. 
which carries a traversing piece, E, with a guide point on one end 
directly opposite and tike the one In the upper bushing. These guldea 
(It the hole In the work, which la advanced or withdrawn by means 
of the screw P, which is fastened to the piece E by the pin, O, Intro- 
duced in such a location that the side rests in a round groove on tbe 
upper end of the screw, attaching It thereto and at the same time 
permitting It to rotate freely. Tbe end of a small pin, H, entera a 
spline In the side of E and checks any tendency to revolve when the 
screw la being turned. A knurled head Is pinned and riveted on the 

DrtUlns • 


end of F. A strip of machine steel, J, of sufficient length to extend 
from top to bottom of tbe jig, la seated in a reclangular milled channel 
and fastened by screws and dowel pins. The side holes are carefully 
located In this sirip, and two hardened and ground bushings for No. 4 
drills arc pressed In. 

When in use. die nork Is slipped on the upper guide point, and, 
when the piece F, is advanced by the hand screw, it Is held drroly In 
place, being properly located In relation to the buahlnga by the center 
hole. The piece la then drilled as in ordinary jig drilling, the finished 
piece being removed by simply looaentng up the hand screw. The piece 
E, with the exception of the guide on Its end, la left aoft for the point 
of (he drills to enter the necessary depth for clearance.* 

• C. II. Rowp, I>ec*niber, \90X 

« No. 3— DRILL JIGS 

Simplicity In Jlgr Dealstt 

Another of the chief characteristics la Jig design, which should be 
ftlmed at as much as possible. Is slmpUcity. It Is comparatively easy 
to deelgn a complicated drill Jig lor almost any work, and one of the 
main differences between the amateur and the experienced Jig designer 
Is tbn latter's ability to attain, by Simple means, the same results, and 
the same accuracy, as the former reaches by elaborate devices. 

An example of a simple Jig which performs the work for which it is 
intended as satisfactorily aa a more complicated tool, is shown in 
Fig. 55. The work to be drilled is shown at the top in perspective, 
At .1 Is a '^i-inch tapped hole In a curved surface, as shown ; a a are two 


Vj-lnch holes In (he 
from holi' A. A ca: 
of work inside, was 
boles In Ibe ears. I 
fitted Into 1 

tars, whltb must be 7 Inches from center to center 
t Iron Jig body, of the rlglit size to hold the piece 
made, and bushings 6 ii inserted for drilling th« 
□r drilllnf; the '^^-inch holes A, a cross-piece B was 
Lit In the sides of the jig body and this cross-piece 
carried a bushing, as sho«ii. This croBS-plece was held in place by two 
straps, as Indicated. As the hole had lu bt* countersunk, a combined 
drill and countersink was made, which did bolh operations at one cut. 
The work Is pushed Into the Jig from tbe end. and some clamping 
arrangement, two C-clamps, for instance, will serve to hold It in posi- 
tion while drilling.* 

JlgB for Drilling Bough CastlnKS 

There Is a great difterencf in the principles of Jig design applying 
to pieces of work which have flnisbeiJ surfacra from which (he work 
nay be located, and castings which are drilled directly as they come 

■ I'ruiik C. Uud».ni, May. IW^. 



line, and when they are so aligned. It .is impossible for the hole to 
come out of center on either end of the boss. The simplest and safest 
way to align these holes Is to run a single-pointed boring bar through 
the screw bushing Into the bottom of the Jig, after the screw bushing 
has been fitted to the Jig, the shank of the boring bar, of course, being 
a good fit In the bole of the screw bushing, which has been previously 
lapped to size. On the larger atzes of busblngs, it has been found 
advantageous to use a good quality of machine steel, case-hardened and 
having a smaller tool steel bushing Inserted in the center. When made 

entirely from tool eteel, the distortion la hardening is too great to 
allow a good fit, which is essential on the threaded portion. The bodies 
of the Jig should be made of cast iron, cradle-shaped, and cut out where 
possible, to facilitate cleaning. The covers which hold the screw bush- 
ings should be of machine steel, held In place by means of screws and 

Two examples of Jigs of this clasa are shown. The larger ]lg. Fig. 
57, was designed for drilling the breast drill frame shown Id Fig. 6S. 

The casting Is clamped by the large bushing first, and then the smaller 
bushings on the ends are brought up just tight enough not to cause 
any spring In the casting. There are two holes in this frame which 
must be reamed square with each other. After trying unsuccessfully 
to ream the holes by hand after drilling in the Jig, the holes were 
reamed In the Jig as follows; The hole In the bushing was made the 
exact size of the hole to be reamed In the casting. A drill of this 
size was used to spot the hole, followlDg with a reamer drill, and lastly 
with a rose reamer, making In every respect a satisfactory Job. 

46 No. 3— DRILL JIGS 

biubU caBttngs, plnloDS, spur gears, Bprockete, palleya. etc., tor ream- 
ing or drllllDg. TblB type of Jig 1b used with great succeae In one ot 
the largest manufacturing concerns In Cfaicago. Formerly caatlnga of 
tbe nature Darned were held In a Jig, using a screw bushing mounted 
In a swinging arm to bold the work while drilling; the arm was swung 
around over tbe casting and the bushing was screwed down onto the 
work. Frequently the operator would neglect to screw the buablng 

down tightly against tbe work, with tbe resultant of a bad Job of drill- 
ing and a spoiled piece. In any case there was considerable time lost 
iD operating the Jig. 

The air clamping drilling Jig shown In section in Fig. 63 was de- 
signed to decrease tbe time required to operate tbe Jig and to Improve 
the character of the work done. The cut shows how a bevel gear la 
held. Tbe gear rests on the Inclined face C, and between three chuck 
Jaws. Beneath the casting is a ring, A, having three cam eccentric 
slots which move the Jaws B toward or away from the center when 
the ring is turned by a suitable handle. With this Jig the operator 
needs only to turn an air valve handle to hold the worli- securely and 

48 No. 3— DRILL JIGS 

der top and groove. This makes the air cylinder conTenlently Inter- 
ctuuigeabre with any number of centering derlces, the centering deTlca 
being removed quickly bo that there Is little time lost In making 
changeB. the clamping being a simple matter. The cylinder has three 
lugs K with open slots for bolta, these matching with three lugs on 
the centering device and constituting the clamping arrangement for 
the centering piece. When the centering piece is to be changed, the 
three bolts are loosened, slipped out of the slots, and the centering 
piece Is lifted out and exchanged for another. 

It the drill bushing has to be changed, the yoke O Is taken oft and 

replaced by another, for It Is generally desirable to have a yoke with 


Us own bushing For each job. With small work the yoke simply has a 
bushing driven from the bottom, as Illustrated In the half-tone Fig. 61, 
and the bushing alone presses against the work, but lor larger work, 
which should be held down at three places on the rim, the yoke and 
clamp are connected with a universal Joint as Illustrated In Fig. 63, 
thus insuring equal pressure on the three clamping points. 

Fig. 65 is a centering device, used on the air.cyllnder. In which ther* 
Is a float. This float rests on a heavy spring, and on the float are 
three lugs A which support the gear casting. This device centers the 
casting, while the yoke Is pulled down by air pressure until the gear 
rests on the three stationary surfaces B. The yoke with Its equalizing 
saddle C holds the bevel gear firmly while drilling.* 

m the design of all devices using compresaed air, care should be 
taken to economize as much as possible with the air, making the spacet 

C. BoRiliDit, April, 1007. 


it has to fill as small as possible. In the jig shown this has not been 
thoroughly taken into consideration. The long motion of the piston, 
entirely operated by air, makes it necessary to fill a great space with 
air each time the work is clamped. In such cases it is usually possible 
to move the clamp down upon the work with a mechanical movement 
requiring no air, and then effect only the actual clamping by the com- 
pressed air, in which case it would probably not be necessary to use 
one-tenth the amount of air now used in the Jig 



In the design of drill Jigs there la lUtle save experience and Judg- 
ment to guide the draftsman when determining tbe dimensions of tlw 
drill bushings. This often results Id having bushings for the aanw 
size of drill made witb widely varying dimensions as to length and 
outside diameters. If, on the other hand, some standard ts adopted 

b:omb for vtAHDAsa fixxd jio bqshinqb 

and adhered to. uniformity will be Insured and the toolmaker can mak« 
up bushings in leisure moments, knowing that they will be availablA 
whenever a rush Job of Jig work comes along. Tables 1 and 2, which 
give dimensions of bushings, are now used by a large manufacture 
log concern, and furnish an eiccellent guide tor any draftsman design- 
ing Jigs where no standard has been adopted. 

Table 1 gives dimensions for bushings which are to remain in the 
Jigs permanently, and In making these bushings tbe external diameter 
given in the column B would be made a driving fit In the hole in 


the Jig. Table 2 gives dlmensionB for removable buBtalDge, and In this 

caae th« oatsld« diameter would be made a light eliding fit In the bale. 

In both tables the column A Indicates the size of drill for which the 

VABiM a. stHBitaiOKB roK STANDARD aniovABLB ji 

bashing Is to be used, and the bole In the bushing would be made from 
0.001 to 0.003 Inch larger than nominal Elze. The bushing shown In 
the cut above Table 1 has a knurled head. Of course,, the head Is 
<Hil7 knurled on removable bushings.* 



































■ H, 
































S , 






-.-. n 


































H- A « 






Table 3 glvea the dimensions (or drill bushings for a wider range 
ot drill hImb, according to the adopted standard of a large manufactur* 

52 No, s— DRILL JIGS 

ing concern in Chicago. It will be noticed that the shoulders are much 
smaller than generally used. There is no real need for the shoulder 
of a loose or removable bushing to be larger than is necessary for a 
good finger hold. By keeping the shoulder dimensions down to the 
figures given in the table, a considerable saving of steel is effected 
in the larger sizes, and when this amount is multiplied by the thou- 
sands of bushings necessary in large machine shops, It becomes a 
very important matter. Another feature of economy possible in bush- 
ings is the use of machine steel, case-hardened, which gives as good 
results for some worl^ as tool steel, and of course is far less cOstly, 
both in price per pound and in time required for working.* 

Hardening Small Jig Bushings 

To harden large quantities of small jig bushings without danger of 
cracking under the head while hardening or while driving them home, 
proceed as follows: Put one gallon of fish oil in a suitable metal 
bucket, and place this in a larger bucket of cold water. The bushings, 
strung about six on a wire, are heated in a small blow torch fire to a 
light red heat and are then quickly plunged into the oil, and kept 
moving around until cold. The hardness will depend upon the degree 
of heat given, and this can be so regulated that it will not be neces- 
sary to polish and draw bushings after hardening.! 

• O. C. Bom holt. May, 1905. 

tH. J. Bachmann, November, 1005. 



In the following outline of a system for getting the most out of 
the tools in the shop, the word "Jig** will be meant to include all Jigs, 
templets, fixtures, appliances, etc., which aid in the rapid and accurate 
machining of parts. With such assumptions allowed, the necessity for 
some systematic scheme of management for the use and care of the 
Jigs should be apparent. However, it is not uncommon, even In these 
days, when the Jig Is admittedly one of the main factors Instrumental 
in developing the shops of the past (where machinery was "built"), 
into the shops of the present (where it is "manufactured'*), to find con- 
cerns where the Jigs are given no consideration beyond designing them 
and keeping them in a questionable state of repair. The whole tool 
or jig scheme, however. Is so interwoven with the entire shop that 
the success of a system cannot be dependent entirely upon any one 
person, but upon the co-operation of all. 


1 Jia 

1 " uo 




TWWT DRILLS- •><;. J^-'^,'-!/,' 

tap-H'-io thread machine 







DRILL '%» 



■J ■■ - 


mote:- care must be taken that chips do 
not accumulate in corners of jic. 

note:- do not tighten too MUCH ON SET 


FiflT- 06. List of Parts of JI9, 
and Tools used "v^th same 

Tig. 67. List of Operations 
to be performed 

The tool foreman is the one, after the management, who contributes 
most to either success or failure, and therefore his selection should be 
made with care. This tool foreman, as we prefer to call him, is to the 
modern shop what the head toolmaker was to the old-time shop, and 
his Increased duties and responsibilities entitle him to the new title. 
He should possess executive as well as mechanical ability, and be broad- 
minded and up-to-datp, for to him should be intrusted the tooling of 
the machines, the design, manufacture and care of the jigs, the com- 
plete control of the tool-room and the enforcement of any system the 
management may inaugurate. He will, however, be doomed to only 
partial success, if not absolute failure, without a tool-room system. 

Suitable methods should prevail in the tool-room, or better, in the 
Jig-room, whereby a workman when receiving a jig gets all the neces- 
sary tools to perform all the operations upon the piece that the Jig 
is designed to do. It should not be necessary for him to ask for the 
tools separately, but simply to ask for the jig and tools for such or 
such an operation, designated either by name or number — preferably 
by number — and have them delivered to him complete. By doing this, 
much time will be sayed, and mistakes will often be avoided. This can 


be accomplished by giying each jig all the loose pieces belonging to 
the jig and all the special tools, the same number as the piece they 
are used upon. They should be indexed under this number and kept 
in suitably grouped compartments and the compartments conspicu- 
ously numbered so that they can be easily located. In these compart- 
ments is also kept a list. Fig. 66, 'Showing what constitutes a complete 
set. When a jig is called for, reference is made to the index, if neces- 
sary, the compartment found and the complete set of jig and tools de- 
livered with reference to the list. 

Probably one-half of all jigs are designed to perform two or more 
operations, and when such is the case, to economize in time and often 
to obtain the best results in machining, each jig should have its opera- 
tion sheet. Fig. 67. To illustrate why it is necessary to perform the 
several operations in a prearranged order, take, for instance, two holes 
intersecting at acute angles, such as a shaft hole and a locking rod 
hole, where the locking rod hole drills half out into the shaft hole. 
Ordinarily a workman would drill the larger or shaft hole first, and 
the locking rod hole afterward. This would be wrong, however, for 
the locking rod hole drill upon entering the shaft hole and meeting 
no resistance for half its diameter, would run out, and the hole would 
not be straight. A very handy arrangement is to have the tool sheet. 
Fig. 66, and the operation sheet. Fig. 67, mounted upon opposite sides 
of a cardboard. They should be of some convenient size, to be deter- 
mined by the number of separate items it is necessary to put upon 

It is regrettably too generally the custom to take for granted that a 
p^ece is right if it has been Jigged, and in this way much work is 
often spoiled that could be avoided by the simple system of inspecting 
the first piece of every lot done In a jig and ascertaining Its correct- 
ness. If the first piece is found to be correct, it Is reasonably safe to 
assume that the rest will be. It Is also well to provide printed blanks 
upon which defects and possible improvements in jigs are reported 
to the tool foreman. These are made out in duplicate by the foreman 
under whom the defects, etc., are discovered, he keeping the copy and 
sending the original to the tool-room. This method will be found to 
be superior to giving verbal Instructions, as it is a check from one 
foreman to another. There is an adage which cannot be more appro- 
priately applied than in the case of repairing jigs, and that is, "Don't 
put off until to-morrow what can be done to-day." 

It seems hardly necessary to mention the matter of allowing repairs 
to be made upon jigs In any other place than the tool-room, because 
it is so obviously wrong that every one must see the fallacy of such 
a course and what a demoralized state of affairs It will lead to. In 
this matter there should be absolutely no margin. Whenever repairs 
are necessary on jigs, they should be turned over directly to the tool- 
room, and even the most trivial matters should be attended to by the 
man In charge of the jigs, as he is held responsible for results. 


hold In R vlw while mllllns. As it would proT* quite expenslTe If 
manr Jaws ot this style were made from steel, they may be made 
from cast iron, and a plate of steel placed where the work Is to rest, 
as shown at a. Fig. 1. After the steel plate has been cat to shape and 
the locating device attached, the Jaw may be hardened. If the derlces 
mentioned are pieces which must be attached to the law, or pins which 
enter holes In It, they must be removed when the Jaw Is hardened. 

At times It Is necessary to hold pieces so that they rest on Bhelvea 
on each Jaw, or are located by pins In both the stationary and movable 
Jaw. Genenlly speaking. It U advlaable to construct special fixtures 
for such pieces, provided the degree of accuracy and the number of 
pieces warrant the outlay. How«ver, It the pieces must be held In 

jaws In the vise, some method should be lound to prevent the movable 
Jaw from rlatng when pressure 1b applied, In the operation of "tighten- 
ing up." It the Jaws are reasonably thick, large pins may be used, cme 
near each end of the Jaw, as shown in Fig. 2. These pins must he 
forced solidly into one Jaw and fit closely in the other. Another method 
which works nicely la shown In Fig. 3. In this case the movable Jaw 
proper Is connected with the stationary Jaw by means of pine, or a 
slide of diEFerent design. It Is not, however, attached to the movable 
slide of the vise, but a hardened piece of steel le attached to this and 
bears against tbe movable part of the Jaw. Many other forms are 
made, one of which Is shown In Fig. 4. The front portion hinges at 
the bottom, and Is presBed agatnBt the work by a movable slide. In 
all such holding devices, however, chips are liable to get between the 
various parts, decreasing their accuracy. 

When making any form of holding device. It is necessary to provide 
a place for the burrs that are a result ot previous operations, unless 
they are removed by a process of filing or grinding. In many cases 
these burrs will be removed by future operationn If It Ib possible to 
provide a place for them so that they will In no way affect the accuracy 


of a form shown in Fig. 8. At other times the vise may be used with 
the movable Jaw of the original form, and with the stationary Jaw 
arranged as in Fig. 9. In this case a flat piece of steel is attached 
to the outside of the Jaw by means of screws which are a snug fit in 
holes drilled and reamed in both the auxiliary and stationary Jaws of 
the vise. It is apparent that such an arrangement does not allow great 
accuracy, as the Jaw on the end has no backing, and consequently 
will easily spring, yet there are instances where it answers the pur- 
pose as well as a costly fixture. If milling machine vises are drilled 
for screws that hold Jaws in such a manner that the Jaws will readily 
go on any vise, much valuable time may be saved. If we are equip- 

Flff. 6. A DtfflonltStnMldl* 
Mminir Job 

MmMm^r^^ Xf. 

FItf. 7. ArrMic » iP« n t of Via* Jm 
to Hold Pl«c« Shown tn Vig, O 

ping a shop with new machines, this may be readily accomplished, as 
we may order vises drilled alike and corresponding with some vise 
already in use, and to which a number of pairs of Jaws are fitted. 

Cams or Booentrics for Binding Vise Jaws 

The vises ordinarily furnished with milling machines are opened and 
closed by means of a screw. Unless it is necessary to apply consider- 
able pressure to the piece being held, this form of vise will not work 
as quickly as desirable where cheapness of production is a factor. To 
overcome this objection, vises are made so that the slide may be 
opened and closed by means of a cam and lever, and unless there is 
much variation in the sizes of pieces being machined, the cam will 
cause the work to be held sufficiently firm. The work may be placed 
in and taken out in this way much more quickly than when a vise 
operated by a screw is used. In fact, where such a vise will answer 
the purpose, it will be found as cheap to operate and as satisfactory in 
results as special fixtures; and the Jaws necessary when starting a new 
Job are, as a rule, much cheaper than special fixtures. 

When it is necessary to cut in the vise Jaws the shape of the piece 
to be milled, it may be done by milling with the mills to be used on 
the work, as shown in Fig. 10. The pins, or other appliances for hold- 


As cMt iron is the material used for the base of most fixtures of 
this kind, plenty of the material rightly distributed wiU insure free- 
dom from chattering and uniformity of the product, provided other 
conditions are right This additional weight of cast iron does not 
"^•terially add to the cost of the fixture. As a rule, cast iron does not 
prove satisfactory as a surface against which to bed small pieces when 

MmeUmtrp, N.T, 

Fl|r« 10. via* Jaw mad* to OorrMipond to 81i*p« of Work 

niiUing, and for this reason a surface of steel is generally provided 
for this purpose. 

Examples from Actual Bxperience 

^ig. 11 shows a milling machine fixture used for milling a leaf for a 
vernier rifle sight. It is necessary to have the sides, a a, of the leaf 
parallel to the sides of the slot. The base, b, of the fixture is made of 
c&st iron, the bottom of which is planed flat. It has a slot cut in it 
to receive the tongue pieces which flt the tongue slot in the table. A 
groove is cut in the top surface to receive a tongue on the steel por- 











Flff.U. VlxtnrofbrMIUincBlfl«81gtit 

tion, c. This is attached to the base by means of screws, after which 
the projection d, for the rifle sight, is milled in the machine used. 
This insures perfect alignment between the sides of the tongue, d, and 
the table travel, and in consequence the sides of the leaf are exactly 
parallel to the walls of the slot when the pieces are milled. In the 


cua of tbl< particular pleca of work It wu found neceuaiy to prOTlda 
a Mmewhat complicated contrWatice to hold th« leaf down onto the 
fixture while mlllliig, aa the cut waa rather hearr, compared with the 
■trength of the aldeB of the leaf. But It waa suKgeated that bj revens- 
Ing the cutters and running them down onto the work, rather than 
against It, the cutters would be made to hold the work down on the 
seating surface rather than to tend to raise It. All that waa needed 
then was two screws, the heads of which screwed down onto the leaf. 
To release the leaf It waa necessary to give the screw hut a quarter 
turn, as the opposite sides were cut away to a width a trifle less than 

rlB.ia. T*MlBsib*all«]iiiisiiiof ihsMUltecMacbliiaeaddla 

the width of the slot In the leaf. The only reason It was necessanr 
to provide the screws was that at the ends of the cut the pressure of 
the cutters tended to tip the leaf. 

AUgnment of the MIHIdb' Machine Table 
m order to produce good voti nhen straddle-milling on a slngle- 
■plndle milling machine, it is necessary to have the table travel exactly 
at Tight angles to the axis of the spindle. Should It not do so. It will 
be necessary to either scrape the saddle or swivel the head to get the 
aUgameot The Lincoln type of miller usually has proTlslon for the 
latter adjuatment, but if not, and the saddle must be scraped, It is 
better to acnps the sliding surfaces which bear against the bed, ln> 
stead of the table slides, unless the latter should be so badly worn 


mt of the saddle of a milling machine may be tested 
I of a piece of wire attached to the spindle, aa in ng. IS. 



In this case the bearing surface to be tested is on a bevel, instead of 
standing vertical, and therefore a cast iron block is planed to fit the 
angle portion, the block having a vertical surface for the point of the 
wire to bear against. 

Principle of Oang Fixtures 

Fixtures are many times made to hold two or more pieces of work 
to be machined at the same time, thus increasing the efficiency of the 
machine. Fig. 13 represents a fixture used in milling a bolt head 
flat on opposite sides. The fixture is designed to do away with any 
inaccuracy that might result from an attempt to mill bolts whose 
bodies were of varying sizes. For this reason the grooves for holding 
the bolts are made V-shaped instead of circular. The fixture is so 
designed as to allow the strain incident to cutting to come against 
the solid part of the fixture. To insure ease of manipulation, the cam 
levers, used in clamping the pieces in the fixture, are located in the 
portion of fixture nearest the operator. Were they located on the 

JfacUMry. If.r. 
Flff.ia. Flztor* f6r muiaff Bolt HMkda 

opposite side it would be necessary to nm the table back far enough 
to get the cam levers away from the cutters, so as not to endanger the 
operator's hands. Then again, if located nearer the cutters, they would 
be covered with chips, thus rendering it necessary to clean them every 
time before handling. The designer should always have in mind the 
safety of the operator, not only from a humanitarian standpoint, but 
also because accidents caused through poorly constructed tools and 
appliances are extremely costly to the manufacturing concern in whose 
shops they happen. 

Prevention of Springing Action in Fixtures 

It is generally the best practice to have the device used in binding 
the piece of work to the fixture connected with that part which holds 
the work, as shown in Fig. 14. If this plan is adopted there is no 
danger of springing the fixture and thus producing work which is not 
uniform to gage, as might happen if the design shown in Fig. 15 were 
used. If the fixture is extremely heavy and there is a certain amount 
of error allowable in the gaging, the objection to the method shown in 



Fig. 15 would not be readily api>arent. However, for accurate work 
it is adyisable, when possible, to adopt the method shown in Fig. 14, 
for it is possible to spring fixtures which are apparently quite strong. 
If a fixture is to be made in the form of an angle iron and consider- 
able strain is to be exerted by the operation of cutting, the upright 



Flo* 14 

Fig. 15 

Rg.16 FlQ. 17 

vie*. 14 to 17. TrmirwaXtMkg Springing AuMom in Ylmmmmndnxtofm 


portion of fixture should be made heavy, so as to absorb vibration, and 
it should be well braced on the back to prevent any tendency to yield 
under the strain. If such a fixture were made as shown in Fig. 16, the 
piece of work being machined would be chatter-marked from the vibra- 
tion, and out of true from the yielding of the fixture. If it were made 
as shown in Fig. 17 neither of these troubles would be experienced. 

provided other conditions were right When possible, the pressure of 
the cutter should always be against the solid part of the fixture, as 
shown in Fig. 18, rather than against the holding device, as in Fig. 19. 
One thing that is sometimes overlooked is the inability of the cutter 
arbor to do the work without springing. Many times cutters are made 
with holes so small that the arbor cannot transmit the power without 
springing. If arbors are made for a special Job and are to be subjected 
to great strain, they should be as short as possible. 



Fundamental Principles of Milling Fixture Deeiflrn 

The simplest fixture that will hold the work in a satisfactory manner 
is, as a rule, the most satisfactory, to say nothing of its lower cost. 
It is necessary at times, in order to accomplish a certain purpose, to 
make a complicated fixture, but the more complicated such a tool is, 
the greater the probability of its getting out of alignment and out 
of working condition. There is a tendency on the part of many young 
designers to make elaborate fixtures, not realizing that true success in 
this branch of business depends on making all machines and tools in 
the simplest way possible. To be sure, most of the automatic machin- 
ery on the market is very complex In design, but the designer uses 
every effort to simplify where possible, and still have it accomplish 
the desired result. 

While it is absolutely necessary that milling machine fixtures be 
made In a manner that Insures the desired degree of accuracy, yet 
they should be so designed that the work may be placed in and taken 
out In the shortest space of time possible, since this Item adds very 

Mttkintrjf, Jf. T. 
Flff . 20. Drop Forg»d Jaw, Finished by Milling 

materially to the cost of the article. As it is customary to have the 
operator run several machines, the greater the length of time necessary 
to devote to one machine, the fewer machines he can tend. 

So far as possible the design should be worked out by always work- 
ing to, or by, a given surface, or other working point, and In making 
the fixture the same principle should be adhered to. It Is poor practice 
to change and work from a different working surface unless compelled 
to do so, as any slight Inaccuracy, that in Itself might be of little con- 
sequence, might affect other vital portions. This same principle should 
apply to all machining operations. 

Examples of Practical ApplloaAlons 

As an example of what has Just been said, let us consider the cutting 
pller Jaw shown in Fig. 20. This Jaw was first forged to shape from 
tool steel under a drop hammer. The side marked a was milled first, 
after which the opposite iside was milled. Unless great care were 
taken when seating in the Jaws, the second side milled would not be 



parallel with the first Now, this would not materially affect the fin- 
ished jaw if one particular side were selected and worked to through- 
out the various milling operations. The surface a was selected as the 
working surface and was the one placed against the working surface of 
the drill jig. Then, under normal conditions, the drilled holes would 
be square with the surface worked from. The same side was also 
placed against the stationary Jaw in the milling machine vise when 
milling the surfaces c and d. Then, if the Jaws were properly made 
and set in the vise and reasonable care taken to prevent the presence of 
chips and dirt, the surfaces c and d would be square with a. 

A simple method to use when it is required to mill a block perfectly 
square is to first straddle-mill two sides by holding the block in the 
Jaws of a milling machine vise. The other sides are straddle-milled 
by holding the piece in the simple fixture shown in Fig. 21, so designed 





! • 

I I 



ri«.21. Flxtiir«torStmddl«lCmiii# 

that when the piece is fastened in the fixture, the tendency of the 
tightening device is to draw one of the sides that were milled at the 
first operation down onto the seating surface of the milling fixture 
as shown in Fig. 21. The tilting block 5, bearing at the bottom, acts 
in such a manner that when pressure is applied with the screw it 
forces the work down on the seating surface of 'the fixture, and against 
the upright. It might be found necessary when starting to use a 
fixture of this description to block up under one edge with paper to 
bring the milled surfaces square with the seating surface, as the 
spindle and table of the machine might not stand exactly parallel. This 
must be ascertained by experiment. The parallelism of the two may 
be tested with a height indicator of the description shown in Fig. 22. 
However, if It is found necessary to raise or lower the machine the 
table may not stand in exactly the same relation to the arbor as before 
moving. Then, again, the arbor may not be exactly true. All these 
things must be taken into account when testing machines for align- 


lUUlnc ft Bloyole Bub 
Fl(. 23 showB a bicycle hub haTlng projectlona. Through these pro- 
Jectlona, or ears, are drilled bolea to receive the spokea. The equip- 
ment of milllnK machine! Id the ahop where theae huba were to he 
milled was not sulBcIeDt to turn out the required number of pieces, and 
as it was not deemed wise to Increase the equipment, ways were 

M PuaUalUB of TkbU ai 

derlaed of doing the additional amount of work on the machines on 
hand. In order to accomplish this task. It was found necessary to 
make multiple flitures. 

Two Hzturea were made to go side by side on a plate, each fixture to 
hold a bub. A dog was attached to one end of the hub, the tall of the 

dog entering an opening In the plate on the nose of the Bxture spindle. 
On the other end of the spindle was an Index plate having around Its 
circumference a number of holes equldlstantly spaced, the number of 
which corresponded with the number of teeth to be milled on the 
bub. A hardened steel pin entered these holes and thus located the 
hub. In making fixtures of this character where fine chips can get 
Into the holes. It ts advisable to make locating holes straight rather 
than tapering, since when the holes are tapering there Is a strong 
probability of fine particles getting In the holes on one side of the pin, 
thus causing the work to be unevenly spaced; but where the hole and 
pin are straight. If the pin enters the hole, it must necessarily locate 



the spindle properly. If the holes and pins are properly ground and 
lapped, they will retain their size for a long time. In order to facili- 
tate the pin entering the hole the end should be chamfered somewhat. 
When milling the Job shown in Fig. 23, it occurred to the operator 
that not only could two hubs be milled at a time, but one could also 
make each cutter able to mill the spaces between two teeth each time, 
making a cutter of the form shown in Fig. 24. This shows how 
fixtures and methods are the results of gradual development, and 
almost any operation, however well planned, can almost always be still 
further improved upon. 

Milling a Tapered Square Bnd on an Axle or Tool 
In Fig. 25 is shown a fixture used to mill a square on the end of 
an axle, but with the four sides on a slight taper with the axis of the 


I lllll[f^;^illlliii 


JfatMatqh mf*. 

Fl|r* ^^* Flxtnr* fbr BqnMtnc Bnd of Azl* 

axle. On this account it was necessary to use an end mill rather than 
a face mill, and in order to use an end mill in the ordinary milling 
machine, the fixture must hold the axle in a vertical position and 
with the axle standing at the right angle to produce the proper taper. 
It was found to be impossible to drill the spacing holes in the index- 
ing dial of the fixture with sufficient accuracy by holding it between 
the centers of the dividing head when the holes were drilled on the 
universal milling machine, and it was necessary to resort to another 
scheme. A disk about six inches in diameter was placed between the 
centers of the universal milling machine, and by means of an end mill 



was BQuared. When tested with a square, it was found that the sides 
were not exactly square with each other, however, and they were 
carefully scraped until they were as square as it seemed possible to 
get them. The disk was then placed on a stud located on an angle 
plate attached to the face-plate of a lathe. The indexing dial to be 
drilled was then fastened to the squared disk, and after locating one 
side of the latter parallel with the face-plate, a hole was drilled and 
bored in the dial at the proper location, after which the stud was 

Flff. ao. Axto lfUl*d ta Flxtar« Shown in Flir* 30 

turned so the next side of the squared piece was parallel with the face- 
plate. By continuing this method, four holes were drilled and bored 
that were equidistant from each other. These holes were bushed with 
hardened steel bushings, ground inside and outside, and then forced 
into the holes. Pieces milled on this fixture, and which were located 
by this dial, were found so nearly square that no error could be 
detected when tested with a square. Fig. 26 represents the axle whose 
ends were milled. 

In the previous examples an attempt has been made to avoid using 
complicated fixtures in illustrating the various methods of doing work, 
as they would be more confusing, and the simple fixtures illustrate the 

rv — vn 

FIff.aV. Oa«ttB#tob«]Cm*dlnFlztar«ahownlnV1ff. 28 

methods involved as well. There are certain principles which must be 
observed in designing fixtures of this character. These can be more 
plainly illustrated when simple fixtures are shown, but the designer 
may elaborate as much as is necessary to produce a tool adapted to 
the work in hand. 

Fixtures with Adjustable Supports 

We often have to mill articles of cast iron or other metals which 
are not uniform in size or shape, and which would not locate alike 
in any fixture, without means of compensation for the irregularities. 
It has been noticed that columns of milling machines, which weighed 
400 or 600 pounds, have sprung out of true when on the planer table 
by tightening a holding bolt, when the wrench used was an ordinary 
6-inch wrench, apparently applied with small force. To secure a good 
Job, it is therefore necessary to block under the work very carefully, 
and then fasten it securely for the roughing cut; and for the finish cuts 
the strains on the clamp have to be removed entirely, or nearly so. 



If it is possible to spring a large mass of metal in this manner, it is 
apparent that comparatively weak pieces may be distorted very easily. 
For this reason, it is necessary many times to provide adjustable sup- 
ports at the points where the fastening devices are located, and also at 
points where the pressure of the cutter would have a tendency to 
spring the piece. 

Fig. 27 represents an iron casting, the surfaces of which are to be 
milled. As castings will distort more or less in cooling, and as they 
are very liable to alter their shape when the surface "skin" is removed, 
it is often necessary to provide fixtures with adjustable supports for 

Fl0. S8. Ftztare for Sapportlnff Plec* Shown in Tig. 27 

holding the piece, as shown in Fig. 28. In milling a piece like that of 
Fig. 27, such a fixture should be used when taking roughing cuts on 
surfaces a and Z), and the finish cuts on surface &. 

In the case of work that must be very accurate as to dimensions 
and truth of finished surfaces, it will be found necessary to finish the 
surface a approximately true by means of grinding or scraping before 
milling the surface h for finish. This is especially true with such work 
as the knee of a milling machine, as shown in Fig. 29, where it would 



1 c 






1 j 


■'■-— "■ 


X 1 

^ m 






JTMAbMry. M K. 
FIff. 20. Methods Us^d for ▲ocur*tely Finishing • lOUlnff MaohJae Kne« 

be necessary to rough mill the surfaces a and & and finish mill a. 
After this, the knee should be "rough scraped" to give It a bearing 
against the fixture and to prevent it winding or twisting, as would be 
the case if the surface a were not true and were clamped against the 
fixture. To attempt to scrape these surfaces and get out a wind occa- 
sioned by inaccurate milling, owing to one of the surfaces not being 
flat against the holding device, when the finishing cut was taken over 
the other surface, would cause much needless expense. While the 



above remarks ar« applied directlj to the milling ot k mlllInK machln* 
knef, they are equally applicable to anj piece of work that must ba 
true, and whoae shape or material renders It liable to sprlUK aa a 
reault of some machine operation. 

There are Jobs which require a number of cuts on one side and 
which must be of a certain unl/orm depth from a given nurface. If 
the pieces are of a uniform thickness they may be held In the usual 
manner, by having the under aide of the piece bear agalnet the seating 

surface of the fixture and the cuts taken on the upper side. If, how* 
ever, the pieces are not of a unltonn thickneaa. and the cuts must be 
of an exact depth, some other method ot holding must be employed. 
Ftg. 30 represents a cap used for holding a traveling carriage in place 
on a knitting machine. The V-groove oa must be given depth from 
the surface b, and owing to certain conditloni it Is not practicable to 
mill that surface at the time the grooves are milled. The distances 
from the screw holes must also be equal. 

A fixture of the design shown In Fig. 31 was made to hold the cap 
when milling the V-slots and bevel on enda. It will be observed that 
it is an Inverted fixture and that the surface b of the cap, which has 
been previously milled, rests against an under surface of the fixture. 
Pine which fit the screw boles In the cap project from the seating sur- 
face of the future and enter these holes, thus properly locating the cap. 



a represents the piece of mild steel cut to length; b, after one side 
is milled to shape; and c, after both sides have been milled. Eiglft 
pairs of legs are milled at a time, and at a fraction of the cost of 
drop forgings. 

Fig. 35 shows a case of bridge milling the flat portion at the end of 
a bicycle crank. As in the case of the caliper legs, a double fixture 
is used and six pairs of cranks milled at a time, milling the right- 

"Fig. 33. Principle of Briilff* inning Flxtnr* 

hand crank in one fixture and the left-hand in the other. These 
are located side by side on the same machine. On account of the 
unequal quantity of stock removed at the various portions, a slight 
inaccuracy can be observed, but this is corrected by running the 
cutters across the work twice at the same setting of the pieces. 

In these two examples of bridge milling cited, the milling was 
done with straight cutters, whose teeth were cut spirally, the helix 
being right-hand on one cutter and left-hand on the other, to do away 
with the thrust incidental to long interlocked spiral mills where the 
teeth of several cutters are of the same hand helix. 

Vertical Spindle MiUing 

When surfaces are to be machined flat it will be found more satis- 
factory and quicker, in many cases, to use an end mill of the proper 
design. The work may be held in a special vise or in an ordinary vise 



Fig. 34. Samples of Bridge Milling Cata 

attached to the vertical face of an angle iron, and done in an ordinary 
horizontal milling machine as indicated in Fig. 36. The best results 
in vertical milling are obtained by using a vertical spindle milling 
machine, especially if heavy cuts are to be taken; but unless there is 
work enough to keep the vertical machine busy, it is, generally 
speaking, advisable to buy a horizontal machine with a vertical attach- 


m«nt, since It la poulble to use tbe machine either way, as required. 
The flzturea for holding work when machlnlnE by this method will not 
dlfler materlallr from those already descrlhed. There are several 
advantas«s ol vertical over horizontal milling for many classea of 
work; one vary Important ooe Is that the surface being milled la 
usually more plainly in eight In tbe vertical machine, being turned 

n • aiejel* Or«ak 

upward, than in the horizontal, where It would have to be turned 
inward to the spindle. In order to permit the milling operation fa> be 

Came or Bccentrics for Binding Work in Fixtures 
Cams are applied to vises and special fixtures in a variety of ways 
and furnish a rapid means of binding the work In place. At times 
the cam la very simply made on the end of a piece as shown In Fig. 37. 
If It iB necessary to get considerable length of movement to the slide of 
the fliture, the cam may, be made on a piece having a turned projection 
on Its lower surface, which fits In a hole in tbe base of the fliture. 
When it baa been turned suISctently to relieve the pressure against 

the allde, the cam may be lifted from the fixture and the slide 
moved as much as Is necessary. After placing another piece of work 
in the fixture, the ilide may be moved against It. the projection on tbe 
cam iDierted In tbe hole, and the necessary pressure applied by turn- 
ing the cam. 

Fig. 38 shows a cam which is round In form and has a round pro- 
jection which enters a hole in the fixture. This smaller projection 
is eccentric with the larger. In which a hole is drilled and a lever 
Inserted as shown. This, like the previoni form, may be made remov- 
able if desired. Cams of varlons detlgna may be employed for holding 
work, the particular dealgn depending on the piece to be held. 


Other Bindlnir Devices 

The method employed for holding work in the fixture depends, of 
course, on the nature of the work. Unless It Is necessary to bind the 
work more securely than would be possible with a cam, it is not 
advisable to use a screw, on account of the length of time wasted in 


Fi0. 87. 8iaiipl««t Form of Omaau Bliulor 


Flff . 83. Boo«ntrlo fbr Btndlng Work !a Vlxtarmm 

turning it back and forth sufficiently to secure or free the work. At 
times it is necessary to use a screw, and it is found possible to save 
time by the use of a collar of the description shown in Fig. 39. When 
the nut is turned back part of a turn, the slotted collar may be 
removed and the work taken out, sliding it right over the nut. After 
putting another piece in the fixture, the collar is placed on the screw 
under the nut, and the nut tightened to give the desired effect. 

I'i'i! '|i 


Flff . SO. Blotted OoU»r fbr 
Roloadair Woric Quickly 


Flff . 40. Romovablo Post 

or Stud 

Fig. 41 shows a method, some modification of which may be employed 
to hold work when it would not do to have any screw heads or other 
devices projecting above the strap. When pressure is applied by means 



of the acrew, the portion a is forced down onto the piece of work. 
The angle piece is hinged at h, as shown. At times it is possible to 
substitute a cam for the screw, and so lessen the time necessary to 
operate the device. When forgings or castings are machined, it is 
sometimes possible to take advantage of the beveled portions occa- 
sioned by the draft necessary to get the forging out of the die, or the 
pattern from the mold. If the amount of bevel ordinarily given is not 
ample to insure desired results, a sufDcient amount may be given when 


Holding Work w1mt« Bpi 

la Limited 

the die for the forging» or the pattern is made. Fig. 42 shows a fixture 
holding a casting by means of considerably beveled edges. 

When such a method would bind the work sufficiently strong, it is 
customary many times to use a screw having a right-hand thread on 
one end and a left-hand thread on the opposite end. Two applications 


A B «— r^r 

Flff. 48. DtfBnr«ntl»l Screw XoT«mMite 

of this principle are shown in Fig. 43; at A the screw is held from 
moving lengthwise by means of the block c, and the jaws are moved 
toward or away from each other by turning the screw. The jaw at 
the left, a, has a right-hand thread, while the right-hand jaw, b, has 
a left-hand thread. This fixture is valuable when it is desirable to 
mill a slot, or a projection in the center of pieces which vary in width, 
and where the variation is immaterial. In the fixture B the jaw a is 
tapped with a left-hand thread, and the stationary upright, 5, with a 
right-hand thread. These threads being square in form may be of 
coarse pitch, thus causing the slide to move rapidly. 

T6 save time, it is customary at times to locate the binding screw 
in a removable post, as shown in Fig. 40. When removing the work 
from the fixture the screw is turned sufficiently to relieve the pres- 



sure, and the post lifted out of the hole, after which the work Is 
removed from the fixture, the bearing surfaces cleaned, another piece 
put in place, and the poet again put in the hole, a partial turn of the 
screw binding it securely. In many instances if a screw were used 
in a stud securely fastened to the fixture it might be necessary to 
give it ten or a dozen turns before the work could be removed. 

Fig. 45 represents a device used for holding two pieces of work to 
be machined at the same time. Each piece rests against stationary por- 


ng. 44. Holding Work flrom below by a Oounterbored Hole 

tions o a of the fixture, and is held in place by the swinging pieces b 5, 
which are hinged at the center, as shown, and are closed onto the work 
by means of the pointed screw c which passes through the stud d. 
This stud can turn in the hole in the fixture, and so allow the point 
of the screw to swing somewhat to conform to any variation in the 
thickness of the pieces being held. When pieces have holes through 
them it is possible many times to take advantage of these in holding 
the work. Fig. 44 represents a piece of work having on its upper por- 


Flff. 46. Holdlaff Two Pl«cea of Work mt » Time 

tion a counterbored hole. A pin with a head a trifle smaller than the 
counterbored portion of the hole extends down through the hole and 
through a hole in the fixture, as shown. In the small ead of the pin 
is a rectangular hole. Through this is driven a wedge-shaped key, 
which draws the work solidly onto the seating surface of the fixture. 

There are occasions when an ordinary cam would be objectionable 
and a screw would be too slow, and yet a combination of the two 
works nicely. Fig. 46 represents such a binding device, which is used 



in holding a blank for a spring bow for a machinist's caliper, while 
the ends are bent in a punch press. When the screw is turned down 
into the threaded hole in the base, the V-shaped projection under the 
head passes up the incline on the upper portion of the leaf, forcing it 
down on the blank. When the projection of the screw reaches the flat 
portion at the top of the incline, the leaf has forced the blank down 
solidly to the bending fixture. If the screw is turned more, it, of 
course, continues to descend, and draws the leaf down still more. The 
advantage of this combination is that if a cam does not pass to its 
highest point at the end of the throw, it is apt to Jar loose if subjected 
to vibration, whereas the projection under the screw head passing up 


• — 


Flir> 40. Oombin*d 0*m And 


the incline acts as a cam, when it rests on the flat portion, and con- 
tinues to draw the leaf down as the screw goes into the tapped hole. 
Although a fixture used on a punch press is used to illustrate the idea, 
the same device may, of course, be applied to fixtures for use on 
milling machines. 

The previous paragraphs are only an outline of the fundamental 
principles, illustrated by means of simple fixtures and various forms 
of binding devices. The application must, of course, be left to the in- 
dividual designer who should always bear in mind that simplicity is 
always preferable to' elaboration, provided the simnle device insures 
the desired result. 



In the foUowlne a number of examplea ol mllllag fixture dealgns (or 
deflnlte purposes are given. These fixtures are selected as typical ol 
the various kinds of milling fixtures found In machine shops. Xo at- 
tempt has been made to show only fixtures of the most approved 
designs, but examples Indicating general practice have been taken, 
and attention has been called to the reasons for the special features of 
each design. The names of the persona who originally contributed th« 

Kg. 47. YtH tar BeldlBS ahklta (br E*rw*r MUllBC 

descriptions of the devices shown, to the columns of Machimbbt, hav« 
been given in notes at the foot of the pages, together with the month 
and year when their contribution appeared. 

Vise (Or Holdisff BhaTts fOr Keyway Ulllinv 
One of the simplest designs of fixtures (or the milling machine pre- 
sents Itself In the form of a special vise for holding short shafts and 
studs while milling a keyway. Such a viae is shown' In Fig. 47. Sev- 
eral advantages over the method of clamping either in an ordinary 
vise or directly on the milling machine table, are apparent. Tho 
clamping bolts, holding the device to the table, are never disturbed 
while clamping the shafts, and If the fixture once has been set In allgit* 
ment, It will remain bo. Every shaft is clamped exactly alike, the 
screw forcing Ihe_ shaft Into the Vs bringing every one Into exact 
parallelism, provided, of course, the fixture la accurately set at tha 
start. It is obvious that this device can also be profitably used on tb« 
drill press (or holding shafts and other cylindrical work for drilling, 
and with an adjustable arm added for holding a guide bushing for tb* 
drill, it would prove efficient as a simple adjustable drill Jig. 



the thickness of the head after being milled. Two clamps B were 
made of tool steel, and hardened to prerent bending. These were 
machined to fit the groove, thus keeping them from shifting sideways 
and always in line with the body of the screw to be milled. The two 
binding screws O were also made of tool steel and hardened. 

Two 4-inch side or straddle mills, held apart by a collar of a width 
equal to the diameter of the screw, were used to mill the heads. After 
placing a screw in the fixture, as shown in the cut, the fixture was 
placed in a vise on the milling machine, the straddle mills being 
set to the clamps for position sidewise, and Just touching the body 
of the fixture for the vertical position. With this fixture it was 
possible to mill the heads with only one cut, and it was found quite 

M^cMmtrf, /f. r. 

Plff.40. Flztur* for IfUllnff Bolt H«*da 

satisfactory. While, however, it was possible to mill the screws in 
this manner so that the result was satisfactory, mechanically, it does 
not say that this fixture was satisfactory economically. If there were 
but a few screws to be milled as indicated, then, undoubtedly, a simple 
fixture like the one shown was preferable. But if there had been a 
great quantity of screws upon which this operation had to be per- 
formed, then a fixture milling one screw at a time, and requiring first 
the tightening of the two screws C, and then the tightening of the 
milling machine vise, would not have been in place. In such a case 
a fixture permitting a great number of screws to be clamped simul- 
taneously, and to be milled all at one time, although more expensive 
to make at first, would in the long run have proved cheaper. A fixture 
employing this principle is shown in Fig. 50. 

The purpose of this fixture is not the same as that of the previous 
device described, but the principle may be employed for almost any 
kind of a milling fixture for small work. The fixture shown in Fig. 50 



Is used on a milling machine for slotting pieces such as shown at A, 
and also for slotting screw heads. The vise jaws Q and H are made 
out of tool steel, and are left soft; they are placed in a milling 
machine ylse, and the piece A to be slotted is placed between the two 
jaws, as shown. The chamber (7 is a cylindrical hole into which are 
drilled holes from the side for the cylindrical plungers D. The cham- 
ber C is filled with tallow, and, as the pieces A are clamped in between 
the plungers D and the vise jaw O, the tallow provides an equalizing 
effect until all the parts are held equally firm. This means permits 
pieces of a slightly uneven length to be held securely. The plungers 
D must, of course, be a very good sliding fit in the holes running down 
to the chamber C. The pin E simply serves the purpose of locating 
the piece A by entering the hole in its center. The holes F are tapped 
to receive screws holding the jaws to the milling machine vise. Pieces 
E and D should be made of tool steel and hardened. When screw 






Fiff. 60. Bgnallirfng Vis* Jaws 

heads are slotted, the parts K and L are used instead of D and E, 
The screws are then held in the semi-circular grooves 3f. the operation 
of the device being the same as when slotting pieces A. The screws 
/ in the ends of the circular chamber C simply serve the purpose of 
preventing the tallow from escaping at the ends.* 

Fixtures for Slotting Screw Heads 

While the fixture in Fig. 50 is, at times, used for slotting screw 
heads, it is not primarily intended for this purpose. In Fig. 51 is 
shown a fixture which is designed for this work exclusively, and which, 
although simple, is an excellent device for holding screws for slotting 
the heads. It has the great advantage of holding each screw with the 
same grip, no matter If the diameters are not uniform. It consists 
of the angle plates C and D, both having tongues underneath to fit the 
slot in the milling machine table, and in D are fitted the binding screw 
E and the guides B, which latter are securely fixed. The guides carry 
the V-blocks A, between which the screws are clamped The guides 
slide freely through the holes in the angle plate C, and may be made 
whatever length desired to accommodate the number of V-blocks and 
screws. If the full capacity of the jig is not required, say only four 
screws are to be slotted, as shown in the cut, the angle plate C is 
moved toward D, so that the binding screw E shall be long enough 

* S. OIlTor, September, 1007. 


to chunp the scnwB. In tect, the arrutgemeiit Is b moat flexible one, 

and should prove a very satlafactory flxture lor any shop. 

A rather InteregtlnK and suggestive slotting device, tbe principle of 
which can be applied to a variety ot work where it is necesaarr to slot 
many pieces with rapidity, la shown In Fig. G2. Tbe part A Is a cast 
Iron block, which Is bolted and keyed to a hand miller, and B la a post 
which swivels In A. At C Is shown & lever wltb Its fulcrum on the 
pin D. The Jaw E Is hinged to the lever and Is held In a closed posi- 
tion by means of the spiral spring on the round bead screw F, the ten- 
sion being controlled by lock-nuts. The tool steel plats O, on which on* 

end ot the piece to be slotted rests, la screwed and doweled to the Jaw 
E. The spring H holds the end of the lever down clear of the cutter, 
when It Is not In operation. 

The fixture Is first brought clear of tbe cutter by moving the machine 
table back; the Jaws are then swung out from the machine, bringing 
the Jaw E agalcet the pin J, which compreBses the spring on F and 
thus separates the Jaws, bo that the piece to be slotted can be put in 
between the six locating pins. The pressure being then removed from 
the spring allows the latter to bind the piece securely In place. The 
lever Is then swung so that tbe Jaw E comes up against the pin J, and 
the lever Itself rests on stop K. The table is then fed forward, bring- 
ing the piece against the bottom of the cutter, which slots It to ths 



dMlnd dapth. The plec« !■ raleased by a reversal of these operations. 
TUaflzUm haa prared satiafactOTT. as It la possible when the machlms 
la readjr for operation to turn out 3D0 pieces per hour. The prlncipl« 
at this lixtore oould be tued tor slotting screws.* 

In Flc SS Is shown another derlce for slotting screws. This Is more 
•labocate, and permits of a continuous operation, the operator placing 
the screws to be slotted In the fixture slmultaneoualy with the slotting 
of the screwi prerlonslr put In. At A and B are shown two rings of 
machine steel, case-hardened, with holes drilled on their peripheries 
■nltable to grasp the work to be slotted. The number of holes will 
Tsrr according to the speed at which the fixture Is run and the work 

being slotted. The rings are held and located on the holders C and D 
by screws and dowel pins not shown in the cut. Holder D la driven 
by means of a belt from the countershaft to srooved pulley E and 
through spur gears F and O and worm and worm-wheel H and J. 
Holder D Is made In one piece wttb the norm-wheel shaft. Holder 
la In turn driven by holder D by means of plna K. held In holder D. 
Spring L takes care of any variation which may exist In the size of 
the pieces being slotted. 

To locate and drill the holes, which retain the work, In rings A and 
it. they are screwed and doweled on the holders, and the fixture placed 
on a drill press In such a manner that an equal section of the hole 
will be drilled In each ring. The rings are then case-hardened. For 
dlOerent pieces of work It Is merely necessary to make different 
rings to salt the conditions of the piece. The bracket 3t Is adlustable 
forward and backward to allow different thicknesses of rings to b« 

,. HcDooald, Nora: 

cr, 1907. 


used. The hole in bracket M is bored at an angle of 2 degrees, and 
the plate A is also faced off at the same angle, so that it will be 
parallel to ring B at N, By boring the hole at an angle, it will be 
readily seen that at point the space between the two rings is 
the greatest, and at point N the least. In operating the fixture, it is 
placed on the milling machine so that the slotting saw will pass 
directly through the center of the screw head to be slotted, and directly 
over the center of the rings. The fixture is then started, and the 
operator only inserts the work in the holes. As will be seen, the piece 
is gripped firmly while passing under the saw, and automatically 
dropped when reaching the bottom.* 

Fixture for Splitting Work In Two Parts 

Sometimes a simple operation like splitting a piece of work in two 
will be found to present difficulties equal to those encountered in 
much more complicated operations. One such a case was met with in 
machining the pieces shown in Fig. 54, which were to be split in two 
along the line X-X. Owing to the peculiar shape of these pieces it 
was impossible to clamp them, by simple means, in any position so as 
to mill more than a single one at a time, and as a large quantity were 
to be made it was desirable to arrange so as to cut a number at a 
single operation. For this purpose the fixture shown in Fig. 55 was 
constructed and with this ten pieces could be cut at a single setting. 

This fixture consisted of a casting A which was provided with a 
tongue for aligning it upon a milling machine table, and a slot at 
either end for receiving a clamping bolt. A series of holes, of the same 
size as that in the work, was drilled in the upper part of the fixture, 
and to insure their being parallel with the tongue, the drilling was 
done in place upon the milling machine, the vertical attachment 
being used. These holes were fitted with the studs B, which were 
of sufficient length to extend through the work C, as shown in the sec- 
tion. On the bottom of each stud was placed a split washer and nut, 
the latter being small enough to pass through the hole in the Jig and 
work. These studs were prevented from turning when the nut was 
tightened, by means of a set-screw D, the point of which fitted a slot in 
the side of the stud. A similar slot was also cut in the side of the 
nut so that it could pass the set-screw. A slot E, the width of the 
splitting saw, was cut through the top of each stud, and the set-screw 
D insured this slot being always in proper position for the saw to pass 
through when splitting the work. 

Before the pieces were placed in the jig, they were bored and faced 
on the top, bottom and on the straight sides, so that the splitting 
formed the last operation. Ten of the pieces were placed on the fix- 
. ture, the bolts B put through and the washers put in place. Before 
tightening the nuts a straightedge was placed along the front side of 
the pieces so as to set them all squarely, after which the nuts were 
tightened and the saw passed through the group in the usual manner.** 

* Fred R. Carstensen, September. 1907. 
** Charles P. Thiel, August, IOCS. 



Slottinff Fixture tor Special Chuck 

The piece shown in the upper right-hand corner of Fig. 56 is a latch 
chuck, made of cold-rolled steel, and used on a special machine for 
holding the ends of rods. The body and the center holes on both ends 
are turned in the lathe and the other holes are drilled in a special Jig. 

The fixture shown in Fig. 56 was designed for holding the chuck 
while milling the longitudinal slot to receive the latch, which was re- 
quired to be exactly central with the axis of the piece. While not of 
unusual design, it possesses some advantages that make it especially 
useful when it is necessary to perform milling operations of this 
nature. It is so made as to be free from any outside incumbrances, 
and the parts where wear is likely to become appreciable are hard- 








1 t-.-i 

1 1*1 

! ! :: 

■ -^ 





....._• 1 





FUr. 60. Blotting Flxtar« Ibr a 8p«olAl Ohuok 

ened. The principle applied to the clamping mechanism is that of a 
gradual wedging action, thereby holding the work securely, and at the 
same time pern?itting the quick removal of one piece and the inser- 
tion of another by simply turning the knurled knob to the right or left 
as may be desired. As will be seen, the clamping mechanism is 
entirely enclosed, thus avoiding dust and dirt, and lessening the liabil- 
ity to accident from any external cause. While the illustration shows 
only one way in which this device may be employed, a wider field of 
application will without doubt suggest itself, as it is suitable for hold- 
ing all kinds of milling Jobs, especially where the work is polished and 
would be marred by clamping in a vise in the ordinary manner. 

The fixture is made of liberal proportions, to insure rigidity, and is 
tongued and slotted for clamping bolts. Through the center of the 



first But tblB means a good many measurements, bolts, straps and 
settings of the machine, the mass of which mar be avoided by th« 
fixture shown. It consists of a casting B to wbich the work Is fast- 
ened In any convenient way after being loc&ted hy the spots e e". i i 
and a' m", which are finished to tbe dimensions of the finished work, 
and serve to show tbe necessary position of the work In order to 
clean. Tbe fixture has on Its lower elds a key slot K corresponding 
to the slot in tbe machine platen and spaced equally between the oppo- 
site spots ■ ■ and t' ■' on the side. 

In setting up the machine, the fixture Is located by tbe key, and the 
cross-feed screw Is nsed to bring tbe spots > < or «' r to the line of cut 
of a face mill on tbe spindle nose. As the slot ft is located centrally 

between the sides to he milled, the esme Betting ol the machine an> 
swers for both sides, It being necessary only to turn the fixture around. 
The ends are placed In poBltton In the same way, and without altering 
the setting of the machine, for tbe slots m m' near the ends of the 
fixture are the same distance from surfaces e e* as la slot k from sur- 
faces M • and >' »'. Therefore, the operator has simply to see that Uw 
key enters the slot properly. 

Ears may be provided tor receiving the bolts which, when loosened, 
may simply be moved to suit tbe new position of tbe fixture as It Is 
swung around. In practice one aide may be milled first and then one 
end, the other side, and tbe other end; one rotstlon completing the 
piece. On many kinds of work the key and slots would not be accn- 
rate enough. In which case a base plate upon which the fixture might 
be located by dowels could be brought Into service. The prlncipla, 
however, would remain the same. 

Simple But Efficient Millinfir Fixture 


Figs. 68 and 69 show a piece of work, and the method employed for 
finishing the bosses on same by milling. In Fig. 68, which shows the 
work, the surfaces finished are indicated by the letter /. The fork end 
of the work is finished by the cutters A, B, and C, Fig. 69, while the 
other end is finished by the cutters Z>, E, F, and A, in the same figure. 
In Fig. 69 is also shown a plan view of the deyice which supports the 
work when being milled, as well as a side view of the device. It will 
be seen that the fixture for holding the work is very simple, consist- 
ing simply of three V-block supports, one at G supporting the casting 
near the fork end, and two at H supporting the hub at the other end. 
There are two vertical standards K which are mortised for a key 
which clamps the work down on the V-b locks. The particular feature 

3tacKiniry,y. T. 
Fig. 68. Thft W^ork to b« MlUed !n the Flztor* in FIff. 00 

of this device is that the V-blocks are located at such a distance from 
the center that, when the hub is milled and finished, and the upper 
plate of the Jig revolved one-half of a revolution, the center cutter A, 
which has been previously employed for finishing one side of the hub, 
will be in correct position to mill one side of the fork end, the spac- 
ing collars between the cutters, of course, being made to take care 
of the required distance. A stop pin is used for keeping the upper 
revolving plate in the correct position in regard to the lower bed-plate. 
A milling fixture of this description can be used advantageously on 
a great number of pieces which are ordinarily Jigged two or three 
times. One great advantage inherent in this class of fixture is that 
the work is finished at one setting, thus insuring that all the machined 
surfaces are in proper alignment. Another advantage is that the work 
is handled only once at the milling machine, while if milled in the 
usual way, the hub end would be milled with a straddle mill, and then 
the casting taken to the drill press, and after the drilling operation 
returned to the milling machine for finishing the fork end, the work 
being probably held in another milling Jig and located by a pin or 
stud through the hole in the hub.* 

* T. Zieg ler, November, 1008. 


A4]uatebl* HiUinff FlxturM 

Otten, wlien a number of dlfCerent sizes ol Rome work, shaped and 
flulshed ln<ttae sune or similar waya. are to be milled. It Is possible to 
make mllllDK fixtures, which with slight modifications and adluatmrats 
may serve tor all th« varlotu aUes ot the work, saving the expense 
of a KTeat number of different fixtures. Such fixtures may be termed 
adjustable mltlfas fixtures. They can often be made In a very simple 

The casting shown in Fig. 60 strapped to the table of a milling ma- 
chine Is one of a large variety of housings of widely varying shapes 

and sizes, which are used In the construction of a certain automatic 
machine. These bauslngs resemble each other In that they are pro- 
vided with a V-groove at the bottom, where they are clamped to the 
bed of the machine, and also In the fact that they are made with vari- 
ous pads and bosses, similar on both sides, which have to be milled 
ofl to a uniform thickness of 114 Inch. The cross-sectioning in the 
plan view distinguishes the finished areas. The large number of pat- 
terns used would have made the Job of providing a separate fixture for 
each style of casting a very costly proceeding. Therefore the follow- 
ing sectional fixture was made, and has proved to work well on all 
the different pieces on which It has been tried. 

Fig. 61 shows the different parts of the fixture In detail: A la a 
block with a set-acrew and spur, similar to that used on a planer; B 
Is an abutment provided with a steel block to enter and hold down 
the V-groove edge of the casting; C Is a simple stop to take the throat 



of the cut; D is a wedge used under springy places in the casting; and 
17 is a spring-Jack used where convenient for a similar purpose. In 
Fig. 60 a typical casting is shown on the milling machine platen with 
the various holding pieces arranged ahout it. The two blocks B are 
placed at the outside edge of the table, and the work is supported on 
these and the spur block A, thus giving a three-point bearing for a 
foundation. The spur holds it down on one side, and the steel blocks 
in the V-groove hold it down on the other. Blocks C with their set- 
screws are arranged as shown to take up the end thrust in each direo- 





hutrntrUt Pr—», N. A 
Fiff. 61. D«taUa of A(!Uustabl« Fixture shown with Work in Fiflf. 00 

tion, and wedges D are slipped lightly into contact with outlying cor- 
ners of the work where support is needed. Spring-Jacks E are also 
located where the work is most liable to spring under the influence 
of the mill. These Jacks are fastened permanently in place, the set- 
screws loosened, then the work is pressed down into place and fast- 
ened with the spur block A, The set-screw, which bears against the 
teat of the spring plug, is then clamped, and the casting is thus sup- 
ported without the possibility of the casting being sprung as it would 
be if fastened down onto a solid bearing which might or might not be 
of the right height The set-screw may be placed in either side, as 
convenient, as shown in detail of spring-Jack in Fig. 61. 

A 6-inch end-mill is used in the vertical milling attachment to make 
the surfacing cut. This does its work more rapidly and with less 



When In use, the fixture li clamped to the table ot a lam unlTeraal 
miller, and thli la then adjusted until the vork receivers or holders 
are In the relatlre positions to the cutters Illustrated In Flsa. SG and 
M. The caatlnsa are located In the holders; the eccentric lerers ars 
pushed downward, as shown In Fig. 68; and the castlnxs are thus 
clamped In position. The toed Is then thrown In and the table and 

Fixtures for MilUns a Journal Cap and Base Plat* 
Simplicity In Jig and flzture design is one of the most Important 
fundamental principles. It Is not necessary tbat a dxture be elaborate 
to be efficient. On the contrarr. It Is often the case that the simpler 
fixture Is by far the one to prefer, as It has less parts to repair, and, 
when repairs are needed, they can be carried out with leas trouble. 
The following description of tools used In the milling machine tor 
flnlBhlng a journal cap and base casting, gives a few InstructlTe exam- 
ples ot Bimpllcity in fliture design coupled with efflclencr. 

Taking the cap first, we majr hold It In the manner Indicated In Fig. 
67. If we are manufacturing a large number of these pieces It will 
par to make special fixtures for arranging them so that the extreme 
length ot the table feed or travel may be used. We may arrange to 
take one or more rows of the castings side by side, depending on the 
size of the miller. The cap will be seen to be resting on pins where 
the bosses for the cap bolts come, this making a convenient and relt- 

• JoMpb T. Woodworth, Jaly, IMS. 


same that has been said regarding the operations on the cap may be 
applied to the base. Fig. 68 shows how this piece would be held. The 
clamps hold down the piece, while the piece is blocked up against a 
liner to insure a setting parallel with the travel of the table. The row 
is kept from shifting endwise by using the hunters mentioned abore. 

^facMiwry. If. T. 

Flff. 68. Holdinir the Bas« of Bearing whUe MUllnir Seat for 0»p 

In machining the foot of the base piece we are confronted by a Job 
that presents a kind of milling operation which has many little points 
of interest. The problem of milling comparatively broad surfaces is 
presented. It is an acknowledged fact that the milling of such surfaces 

MmtKxntr^ .V. Y 

Flir< eo* Biaiple Holding Devioe used when EHab Milling the Lower Surfltoe of the ] 

must be accomplished by cutters that are so constructed that the chip 
is broken up into short cuts, giving the operation the advantage of the 
single pointed tool in the question of power required, and truth of 
surface obtained. This is accomplished by notching the teeth of the 
cutter so that they may be presented to the work successively, both 


notches and teeth being cut aplntl at rlgbt angles with each other. 
A surface produced br such a cutUr will bear the strictest ezamlna- 
ttona aa to truth. 

Fig. fi9 shows one method of machining the bottom surface. In this 
method ve use a plain milling cutter as shown, taking one or two 
cots as the case may require. If verr lUtle stock has to be removed 
but one cut ought to be sulBcIent, as the resulting surface will be good 
enough for the Intended purpose. As will be bcmi the piece Is held 
down and prevented from morlng sideways br the screws which are 
tapped through the strips bolted to the table. This makes a conven- 
ient method and one that will be found to answer the purpose very 
well. Another method of performing the operation le by the use of 

an end mill as shown In Fig. 70. This means of removing the metal 
Is very efficient, as a rery true surface can be obtained with a much 
faster feed and deeper cut than can be done by slab milling. The 
power necessary to revolve the cutter and force the feed Is also very 
much less than that used for slab milling. While the surface may be 
badly marked It will yet he almost absolutely true. When the work is 
set up on the edge as shown, no trouble Is encountered with the cblps, 
as is otherwise the case. We are fortunate In finding this piece to be a 
very easy one to provide Jigs for, as it permits Itself to be set In almost 
any position. The method used In Fig. TO Is a good one, and will be 
found very convenient The top clamp Is removed when the work has 
to be removed or placed In position. Tbls clamp aerves the double 
purpose of holding the work and of setting It in line, the screw being 
used to make any allowance tor variations In the castlnga. When tbia 


method is chosen the machining of the bottom should be done before 
the cap bearing is milled, as this gives a good solid setting for the 
latter operation. A great many operations may be accomplished by 
this latter method, which are now milled with plain cutters. Tha 
action of the cutter in this operation closely resembles that of the 
single pointed tool and has all the advantages that are claimed for 
this tool, but very few of the disadvantages, it being a multiple cutter, 
which means greater output. 

The last four cuts shown leave considerable to the imagination, as 
they show but an end view of the work. This is done because the 
same method may be used to advantage in holding one or a dosen 
pieces. Elaboration of the idea does not seem necessary, since the 
principle is shown.* 

• John Edgar, NoTemljer, 1906. 







By Lester 6. French 

Third Revised Edition 


Matter, Work, Force and Power 3 

Friction 7 

Gravity 11 

Moments 17 

The Mechanical Powers 21 

Graphical Representation of Forces - - - - 26 

Motion and Mass 28 

Falling. Bodies 33 

The Pendulum 35 

Energy 37 

Cbivrisht, 1912; The Induitrlal Prwi. PubHthera of Hagbinbrt 
48-56 Lafmrette Street, New York City 


cule$, which are separated from one another by distances that are 
great compared with their sixe. These molecules are so minute that 
it is impossible to detect them, eyen with the most powerful micro- 
scope; but there are many facts determined by expeHment, that make 
their existence seem very probable. If the speculations of scientists 
are correct, at least 500,000 molecules could be placed in a row betweoi 
the measuring surfaces of a micrometer caliper, when it is set to read 
0.001 inch. A molecule is the smallest portion of matter that can 
exist and still retain the properties of the substance of which it is a 

It is believed, further, that every molecule contains two or more 
indivisible portions of matter, called atoms. Thus a molecule of water 
is composed of two atoms of hydrogen gas and one atom of oxygen 
gas. A molecule can be separated into its atoms by chemical action 
only, and then the separation is only momentary, for the atoms at 
once combine to form other molecules, usually of a different nature. 
The atom is purely a chemical unit; we are not concerned with it in 

Molecular Forces 

Two opposing forces reside in the molecules — an attractive force 
that binds the molecules together, and a repellent force, that tends to 
push them apart The three states of matter, solid, liquid, and gaseous, 
depend upon the relation of these forces. If the attractive force pre- 
dominates, the body is solid; if the repellent, it is gaseous; if the two 
are nearly balanced, it is liquid. 

The repellent force is probably one manifestation of the phenomenon 
which we call heat. Thus, when a bar of steel is heated, the attractive 
force is gradually overcome by the repellent force, as is seen in the 
expansion and finally in the melting of the bar. So, also, if we heat a 
piece of ice, the ice is turned to water, and at last, when the repellent 
force becomes very strong, the water is turned into steam. 

The attractive force is capable of acting not only between molecules 
of the same kind and in the same body, but between the surfaces of 
different bodies which are in contact, as well. In the former case it 
is called cohesion, and. in the latter, CLdhesion. It is cohesion that 
resists any attempt to pull apart a body, like a string or a wire, and 
adhesion that holds together bodies that stick to one another, as in 
the case of two pieces of wood, when united by glue, or of drops of 
rain on a window-pane, pencil or ink marks on a piece of paper, etc 
The effect of adhesion is usually more noticeable between solids and 
liquids than elsewhere. Neither force will act, except at insensible 
distances. To join two pieces of iron, for example, welding must be 
resorted to, in which process the hammering brings the molecules in 
the two parts near enough together for the cohesive force to take 
effect. Adhesion and cohesion are of the same nature, the difference 
between them being one of name or definition rather than of kind. 
Two absolutely smooth surfaces, if such were possible, would adliere 
to one another perfectly, since their contact would be perfeet, and it 


this diatance, and which acts in the direction of the arrow, is less 
than the weight W, and hence, if W were multiplied Xxj I, the result 
would he too great If it were known, howerer, what force, acting in 
the direction of the arrow, was required to roll the ball, then this force, 
multiplied bj ), would give the work. 


From what has been said upon work, it is plain that a force, how- 
•Tsr small, can perform any required amount of work, provided time 

Ma«Mn*mJf T» 

Fl«. 1 

enough be allowed. A toy engine, for example, might do 1,000,000 
foot>pounds of work in a few hours, while an engine of moderate pro- 
portions would accomplish as much during a few strokes of the piston. 
Foot-pounds of work, merely, with time left out of account, would 
form no basis by which the capacities of the two engines could be com- 
pared. Hence, to compare the work done, either by or upon some 
agent, the time required must be considered. 


rig. a 

The term pother is employed to indicate the quantity of work done 
in a given time. "One million foot-pounds" is an expression indicating 
work; 1,000,000 foo^pounds of work performed in a day, or an hour 
or minute indicates power. Work has the two elements, force and 
the distance through which the force acts; power has three elements: 
force, distance, and time. 

'The unit of power adopted for engineering work is the hone-power 
(abbreviated H.P.). One horse-power is equal to 83.000 foot-pounds 



adhesion can generally be neglected, and the whole resistance consid- 
ered as the friction. 

Kinds of Friction 

(a) A distinction is usually made between Iriction of rent and frio- 
Hon of motion^ the former being the frictional resistance to be over- 
come in starting a body into motion, and the latter the resistance that 
continually accompanies the motion. Friction of rest is generally 
greater than friction of motion, other conditions being equal. 

(2)) When friction is mentioned, sliding friction is understood, i.e., 
such as that between an engine crosshead and its guides, or between 
a journal and its bearing. It is due to the roughness of the surfaces 
in contact Whenever wheels are employed, or rollers or balls placed 
between the surfaces, the resistance is called rolling friction, the 
nature of which is somewhat different; it is then due to the fact that 
the rolling body makes a greater or less depression in the surface of 
the other, so that it has continually to rise out of a hollow, as it were. 

(c) Frictional resistance also occurs between the molecules of 



FIff. 3 

Flff. 4 

liquids and gases, or between them and any solid body with which 
they may be in contact,, as in the case of air when blown through a 
pipe, or a ship when sailing. This kind of resistance is called fluid 
friction. Its action is very different from that of the friction of solid 
bodies, and it is different in its nature. 

Laws of Friction 

Certain conclusions have been drawn from early experiments upon 
friction, which are known as the laws of friction. They are only 
approximately true, however, and apply only within certain limita. 
Outside of those limits they have been proved by later experiments to 
vary, in some cases very widely. They are: 

(1) P*riction is proportional to the normal pressure between the 

(2) It is independent of the areas, or sizes, of the rubbing surfacea. 

(3) It is independent of the velocity of motion, though friction of 
rest is greater than friction of motion. 

In law 1, by "normal pressure" is meant the pressure in a direction 
at right angles to the surface. If an object rests upon a horliontal 
plane, like the top of a table, the normal pressure is eqnal to Its 
weight If It rests upon an inclined plane, as in Fig. 4, the normal 
pressure (at right angles to the inclined plane) is found by dlTldinc 


of friction &y the normal preMiure. Or expressed as a formula. 
Letting /= the coefficient of friction, 
|'*c=:the force of friction, 
Psthe normal pressure, 

/ = — (4) 


The following coefficients of friction may be taken as aTerag« 
values where more complete tables are not at hand. Under yarying 
conditions a wide yariation from these values may be found, and whera 
coefficients are to be used, they should be obtained, if possible, from 
experiments suited to the particular case. 

Wood on wood, dry. 0.4 to 0.6 

Metals on metals, dry 0.16 to 0.2 

Metals on metals, lubricated 0.03 to 0.08 

Metals on wood, dry 0.5 to 0.6 

Leather on metals, dry 0.3 

If a body is placed on a plane surface, and the latter inclined until 
the body is just at the point of sliding down, the angle made by the 
plane with the horizontal at that instant is called the angle of friction^ 
or the angle of repose. It can be shown that when the plane is at this 
point, its height divided by the base {h-i-h in Fig. 4) is equal to the 
coefficient of friction. This fact affords one means of finding the co- 
efficient of friction of materials by experiment Written as a formula, 
we have, / being the coefTcient of friction, 

/=— (6) 




bodies that are likely to be considered, that these lines of action are 
always assumed to be parallel. The question naturally arises, at what 
point in a body does gravity act? The answer is, at every point All 
bodies are composed of particles, each of which has weight, and conse- 
quently is attracted by gravity. A body, therefore, is really drawn 
downward by a large number of forces of gravity — as many as there 
are molecules in the body. 

It is always assumed, however, that gravity acts as a Hngle farce 
at a point called the center of gravity. In Pig. 5 let the dots p, p, etc., 
represent particles of the body B, under the influence of forces of 
gravity, acting in parallel lines as shown by the direction of the arrows. 
Now, into whatever position this body be placed, there is always one 

I JfoMte«ry,jr.K 
Fiff. 6 

invariable point through which the resultant of the attracting forces 
always passes. This point is called the center of gravity. It is a point, 
as c^, in Fig. 5, at which, if a single force of gravity were to act, in 
place of all the other forces, and equal in intensity to their sum, the 
effect upon the body would be the same as before. Again, since the 
intensity of the gravity force at each particle may be taken to repre- 
sent its weight and the sum of these forces the weight of the body, we 
may consider the center of gravity as a point at which the weight of 
a body is concentrated. 

Center of Oravity 

We have in the previous paragraph given an explanation of the 
meaning of the term center of gravity. We will now consider some of 
the principles involved in finding this point, together with a few of 
their applications. A body suspended at its center of gravity will 
balance in whatever position it may be placed. For this reason, the 
center of gravity is sometimes defined as that point about which a 
body will balance, in any position. Any homogeneouM body will bal- 
ance about its center of magnitude; that is, about its central point. 
Hence, in the case of regular geometrical figures, the center of gravltx 



divides the latter Into two parts, one of which would exactly coin- 
cide with the other. If the figure were folded orer along this line. 
Thus, if the regular pentagon in Fig. 8 were folded ahout the line A 0, 
the parts ABD and AFE would exactly coincide; and if it were 
folded ahout B N, parts BAF and BDE would coincide. Hence, A 
and B N are axes of symmetry, and the center of gravity of the figure 
lies at their intersection, or at G. 

Center of Gravity of Two or More Bodies 

In Fig. 9 let the point O be the position of the center of gravity 
of the two bodies to and W. It must be so situated that they will 
balance about it, if rigidly connected. The turning effect exerted by 
each body about the point G is as though the weight of each were con- 
centrated at its own center of gravity, and acted downward at that 
point as Indicated by the arrows.* Moreover, as will appear when the 
subjects of moments and levers have been studied, if to and W are to 


balance, the ratio of the distances D' and D must be such that, calling 
to and W the weights of the two bodies, the proportion to : D = W : D' 
will exist. Thus, if w = 50 pounds, W, 250 pounds, and D', 25 inches, 

25 X 50 

then 50 : D = 250 : 25, and D = =5 inches. 


The center of gravity lies upon a line connecting the center of grav- 
ity of each weight, and its distance D' from the smaller weight la 
expressed by the formula 

D' = (6) 


where a? = the distance between the centers of gravity of the weights, 

W = the weight of the larger body, 

10 = the weight of the smaller body. 
Stated as a rule: To find the distance D\ multiply the larger toeight 
ty the distance tettoeen the centers of gravity of the ttoo toeights, and 
divide hy the sum of the toeights. 

Center of Qravlty by Trial 

If a body be suspended from a point, or otherwise supported so that 
it is free to vibrate and find its "own center," its center of gravity will 
place itself in the lowest possible position. If a piece of sheet metal 



The case of bodies resting on a horisontal base Is illnstrated in 
Fig. 12. A leaning body, a chimney, for example, would remain in 
equlllbriam so long as a yertical through its center of gravity passed 
within the base, as is the case here with the center of gravity at G. 
Moreover, the equilibrium would be stable, because the chimney, in 
overturning, would act as though pivoted at 0, which is at the right 
of G, and therefore the center of gravity would have to ascend, slightly, 
along aro GA. Should the center of gravity be located at G', the 
equilbrium would be unstable, because, at the moment of overtum- 


Flff. 12 

ing, O' would begin to descend along the arc G'B, With the center of 
gravity at 0", the vertical falls without the base, and the chimney 
would overturn. 

Equilibrium is said to be neutral when, upon moving a body, its cen- 
ter of gravity neither ascends nor descends. Examples: A flat plate 
suspended at its center of gravity; a cylinder, cone or sphere rolling 
upon a horzontal surface. 

(&) A useful application is found in one of the theorems of Pap- 
pus, which is that the volume of any solid which can be generated by 
the revolution of the surface about an axis, is equal to the area of the 
surface multiplied by the circumference described by its center of 



(8) multiply the force by the perpendicular distance from the axis to 
the line. 

This perpendicular distance, as %, J, or / in Fig. 18, is called the 
lever arm of the moment, and the axis or pirot the center of rotation. 
If the force is taken in pounds and the lever arm in inches, the result 
will be in inch-pounds, while if the foot were used as the unit of 
length, the result would be in foot-pounds. Vhe term foot-pounds, 
however, has here a very difTerent meaning from that which has been 
given to it before. In this case it is the unit of rotative eftect, and 

FIff. 18 

in the other the unit of work, or the work done in raising one pound 
one foot high. The two should not be confused. 

In Fig. 18, if the pull along CD should be 60 pounds and the dis- 
tance /, 15 inches, the moment of the force would be 15 X 60 = 750 
inch-pounds, or 


= 62.6 


foot-pounds. If the wrench in position No. 2 should be pulled in the 
direction of the arrow along the line MN, the moment would be the 
product of the force and the lever arm e. When a force tends to pro- 
duce rightrhand rotation, or rotation in the direction in which the 
hands of a watch move, its moment is said to be poHtivCt and negative 
when the rotation tends in the opposite direction. 



librium. Should weight A be increased, the negative moments would be 
greater and the lever would turn to the left, while if B should be 
increased, or its distance from be made greater, the lever would turn 
to the right In the following treatment on the lever some additional 
examples will be taken up. 

Another application of the principle of moments is given in Fig. 16. 
A beam of uniform cross-section, weighing 200 pounds, rests upon two 
supports, R and R\ which are 12 feet apart. The weight of the beam 
is considered to be concentrated at its center of gravity O, at a dis- 
tance of 6 feet from each support. A weight of 50 pounds is placed 
upon the beam at a distance of 9 feet from the right-hand support, K'. 
Required, the portion of the total weight borne by each support. 

Before proceeding, it should be explained that the two supports react 
or push upward, with a force equal to the downward pressure of the 
beam. To make this clear, suppose two men to take hold of the beam, 
one at each end, and that the supports be withdrawn. Then, in order 
to hold the beam in position, the two men must together lift or pull 
upward an amount equal to the weight of the beam and its load, or 


250 pounds. Placing the supports in position again, and resting the 
beam upon them, does not change the conditions. The supports must 
react upwards Just as the men had to pull up. The weight of the beam 
acts downward, and the supports react by an equal amount This is 
an extension of the principle of the reaction of the pivot mentioned 

Now, to solve the problem, assume the beam to be pivoted at one 
support, say at R\ The forces or weights of 50 pounds and 200 pounds 
tend to rotate the beam in a left-hand direction about this point, while 
the reaction of R in an upward direction tends to give it a right-liand 
rotation. As the beam is balanced and has no tendency to rotate, it is 
in equilibrium, and the opposing moments of these forces must bal- 
ance. Hence, taking moments, 

9 X 50 = 450 foot-pounds. 

6 X 200 = 1,200 foot-pounds. 

Sum of negative moments = 1,650 foot-pounds. 

Letting R represent the reaction of support, 

Moment of R = i2 X 12 foot-pounds. 

By the principle of moments, 12 x 12 = 1,650. That is, if R, the 
quantity which we wish to obtain, be multiplied by 12, the result will 


lion. The weight of the valve itself is comparatively small and may 
be neglected. 

The Principle of Work 

There is another principle of more importance than the principle of 
moments, even in the study of machine elements. It is called the 
principle of work, and to make it clear, we will analyze the process 
of the operation of a machine. 

1. A force such as the pull of a driving belt, or the pressure of 
steam, is applied in a given direction at one or more points. The 
product of the force, and the distance through which it moves, meas- 
ure the work that is put into the machine. 

2. The applied force is transmitted to the point where the opera- 
tion is to be performed. During the transmission the force Is modi- 
fled in direction and amount, partly by the arrangement of the mech- 
anism and partly by the resisting force of friction, which it must 

3. At the point where the operation is performed, the modified force 
overcomes a resistance in any required direction, such, for example, as 
the resistance of metal to a cutting tool. The product of the resis- 
tance, and the distance through which it is overcome, measure the 
work done by the machine. 

The principle of work states that, neglecting frictional or other 
losses, the applied force, multiplied by the distance through which it 
moves, equals the resistance overcome, multiplied by the distance 
through which it is overcome. That is, a force acting through a given 
distance can be made to overcome a greater force acting as a resis- 
tance through a less distance; but no possible arrangement can be 
made to overcome a greater force through the same distance. 
The principle of work may also be stated as follows: 
Work put in = lost work + work done hy machine. 
This principle holds absolutely in every case. It applies equally to 
a simple lever, the most complex mechanism, or to a so-called "per- 
petual motion" machine. No machine can be made to perform work 
unless a somewhat greater amount—- enough to make up for the losses 
— ^be applied by some external agent. As in the "perpetual motion** 
machine no such outside force is supposed to be applied, this problem 
is absolutely impossible, and against all the laws of mechanics. 

The Wheel and Axle 

This mechanism, Fig. 18, is simply an arrangement for continuing 
the action of the lever as long as required. So long as a sufficient 
pull is applied to the rope, which fits into the grooved wheel, to over- 
come the resistance of the load attached to the rope that passes over 
the drum, the weight will be raised. 

(o) First we will apply the principle of moments. In Fig. 19, leC 
the larger circle represent the circumference of a wheel of radius R, 
to the periphery of which a force P is applied. Let the smaller circle 
represent the circumference of the drum of radius r, to the periphery 


parU motion la called a driver, and one which receives the motion a 
driven wheel. It can easily be shown that the basis of operation of a 
train of wheels Is a continuation of the principle of the wheel and 
axle. In the latter the wheel Is In realltj' a driven wheel and the axle 
or drum a driver, and hence we have that the product of the applied 
force and the radlue of the driven equals the product of the resistance 
and the radius of the driver. To extend the rule to the wheel train, 
we have that the continued product of the applied force and the radU 
of the driven wheels equals the continued product of the resistance 
and the radlt of the drivers. In calculations, the diameters, or the 
number of teeth In the wheels may be used Instead of the radii, as 
stated above. 

The Pulley 

The pulley, as a machine element, conslste, in Its simplest form, vt 

a grooved wheel or sheave turning within a frame, called a block, by 

means of a cord or rope which passes over It. Combtnattona of these 
blocks are used In order to gain a mechanical advantage In raising 

In Fig. 20 Is a fixed and movable pulley. The fixed pulley A, and 
also one end ol the rope, is attached to the beam overhead, while 
pulley B may be raised or lowered through the action of the rope. 
The distance through which B and hence the weight W move is equal 
to one-halt the movement of the free end of the rope. The applied 
force P, therefore, acts through twice the distance passed through br 
the welglit, nnd will raise an object whose weight Is equal to 2 P, neg- 
lecting, of course, all frlctlonal losses. As the rope passes freely over 
the pulleys, the stress Is the same at every point and Is equal to the 
pull P. Assuming P to be 100 pounds, the pull exerted In either diree* 
tlon by the rope at sections a, h and c would therefore be 100 pounds, 
and hence the forces supporting W would be 100 + 100^200 pounds, 
the pull upon eye-bolt O would be 104 pounds, and the forces actlnc 
at D, 100-4-100 = 300 pounds. 


3ucces8iye coils or helices, equally spaced. The lead of a single-thread* 
ed screw is the distance between like points on successive threads 
measured on a line parallel to the axis of the screw. The amount that 
a screw advances in one turn is equal to the lead, and in fractional 
turns it is equal to the same fraction of the lead. Thus, if a screw 
is given one-fourth turn it advances one-fourth of the lead, and the 
ratio is the same as though the screw were supposed to make one 
complete turn and to advance a distance equal to the full lead. Hence, 
we have for the screw that the applied force multiplied by the circum- 
ference of the circle described by the force equals the resistance multi- 
plied by the lead. 

Machine Bf&ciency 

Thus far in problems of work we have neglected entirely the effect 
of frictional losses, which in many cases require a greater expenditure 
of power than that necessary for the operations actually performed by 
the machine. 

The efficiency of a machine is the ratio of the work got out of a 
machine to the work put in, and is obtained by dividing the former 
quantity by the latter. If 1,000 foot-pounds of work were done by a 
machine in a given time, and 1,000 foot-pounds of work were put in 
in the same time, then the efficiency would be equal to 1,000/1,000 =: 1, 
or 100 per cent; but if only 250 foot-pounds were done by the machine, 
the rest being absorbed by friction, the efficiency would be 250/1,000=3 
0.25, or 25 per cent The efficiency of a machine can never be greater 
than 1. 



A force possesses three prominent characteristics which, when known, 
determine it. They are: its direction, place of application, and magni- 
tude. The direction of a force is the direction in which it tends to 
move the body upon which it acts. If not influenced by any other 
forces, this will always be along a straight line. The place of applica- 
tion of a force is generally, though not always, taken at a point, as 
at the center of gravity. The magnitude of a force is measured in 

Previously we have represented forces which have been supposed to 
act at a given point, or in certain directions, by means of straight lines 
and arrowheads, this being a natural and convenient way to do. It can 
be shown, moreover, that this method serves to represent very accu- 
rately the three characteristics mentioned above. The straight line 
indicates the line of action of the force, the arrowhead the direction 

* IfACHiXTEBi, April, 1806. 


pencil, draw the lines a and b upon the supporting board and com- 
plete the parallelogram Oarb. Then a and b will represent the 
magnitude and direction of the forces acting along A and O B, and 
upon examination it will be found that if the diagonal r be drawn, 
it will extend in the same line as the cord O and will contain as 
many inches as there are pounds in JR. Therefore, r, being opposite 
to C, represents in magnitude and direction the resultant of forces 
a and b. 

The foregoing is an experimental proof of the principle of the paral- 
lelogram of forces, which is as follows: 

If two forces applied at a point are represented in magnitude and 
direction by the adjacent sides of a parallelogram (AB and AC in 
Fig. 25), their resultant will be represented in magnitude and direction 
by the diagonal (AR) lying between those sides. 

As an illustration of the use of the parallelogram of forces, let it 
be required to find the force acting through the connecting-rod of a 
steam engine due to the steam pressure upon the piston. In Fig. 26 
the steam pressure is transmitted through the piston-rod PA, and at 
the cross-head A is resolved into two components, one along the con- 
necting-rod and the other at right angles to the piston-rod. This is 
due to the angle made by the connecting-rod which creates a pressure 
upon the guides. Since the decomposition of the force occurs at A, 
from this point draw the line AiS, representing in magnitude and 
direction the force of the steam pressure against the piston. ' Draw an 
indefinite line A JS^ at right angles to the piston-rod, and from R draw 
R B and R C parallel to AE and A Z>, respectively. Then the points of 
intersection, B and C, will determine the lengths of the component AB 
acting along the connecting-rod, and of the component A C perpendicu- 
lar to the guides. 



Motion Is a progressive change of position. We can Judge of the 
motion of a body only by comparison with the position of some other 
body, which latter does not have the same motion. Motion, then, is 
a relative term. A railroad train running at 10 miles an hour has 
this speed in relation to the earth, but in relation to another train 
moving at the same rate on a parallel track, and in the opposite 
direction, its motion is at the rate of 20 miles an hour. A brakeman 
running from the forward to the rear end of a freight train at the 
rate of 5 miles an hour, might be moving with either a greater or less 
Telocity than this when compared with the ground, depending upon 

* Machikert, Hay, 1806. 


An important application of accelerated motion is found in the caie 
of bodies falling under the influence of graritj; this will be taken up 
later. A body falling freely from rest to the earth acquires during 
the first second a velocity of about 82 feet per second; at the end of 
the second second a velocity of about 82 + 82s=64 feet per second; at 
the end of the third second a velocity of 64 + 82 = 96 feet per second, 
and so on. It is thus a case of uniformly accelerated motion. This 
acceleration, due to the gravity of 82 feet per second in a second (82.2, 
more exactly, for the vicinity of London, and 82.16 for the vicinity of 
New York) enters so much into calculations that it is customary to 
always represent it by the same letter — ^the letter g. 


The mass of a body is the quantity of matter that it contains. We 
are accustomed to think of the weight of a body as a measure of 
its mass. When one speaks of a ton of coal, the word ton conveys 
at once an idea of the quantity of coal that is referred to. We know, 
however, that weight varies with the locality, decreasing as we go 
above the sea level, and increasing in passing either north or south 
from the equator. This fact was briefly explained in the flrst part 
of this treatise. The variation is slight, and in any case could not be 
detected with the ordinary balance scales, but it nevertheless exists. 
If a load of coal should weigh 2,000 pounds at the sea level on a pair 
of platform scales, and should then be drawn to the top of a mountain 
a mile high and similarly weighed, the scales would again balance at 
2,000 pounds, because any variation in the attraction of gravity between 
the two places would affect the counterpoise of the scales in the same 
ratio that it afTected the body weighed. But if the coal were weighed 
in a large spring balance, it would be fo^Ti^ to weigh only about 1,999 
pounds on the mountain top; yet it is perfectly plain that the quantity 
of matter in the coal would not be altered in any way by the Journey. 
We thus see how easy it is, and also how erroneous, to form the idea 
that weight is a correct measure for quantity of matter or mass. 

To obtain a numerical expression for mass, divide the weight of a 
body as determined by a spring balance g, by the acceleration due to 
gravity at that point; or for practical purposes, the weight as deter- 
mined by a pair of good scales, by 32.16. Expressed as a formula: 

ma8S = (8) 


This expression fulflUs the condition required; namely, it gives a 
constant value, wherever the locality. Weight varies directly as the 
force of gravity, and so does the value of g. Hence, if the weight and 
g are both determined at the same place, their ratio will be constant 


for all places. Thus the mass of a 100-pound weight = 8.11 


pounds. On the surface of the sun, where the force of gravity is 28 


a body suddenly into motion or to stop one already in motion. The 
quick start of a railway train throws ererybody against the back of 
his seat, as we say, and in a similar manner the i>assengers are thrown 
forward when the brakes are quickly applied. 

Law II. The term "motion" as here used by Newton embraces all 
the elements that go to make up the motion of a body, and hence intro- 
duces both mass and Telocity, or what is called momentum. The 
momentum of a body is measured by the product of the mass JIf of the 
body by the velocity y, or 

momentum = If 7 = — V. (•) 

It is sometimes defined as the quantity of motion in a body. It is 
not a force, but rather the measure of the effect of a force in a given 
time, since to produce velocity in a mass requires time. 

The second part of this law states that the motion takes place in 
the direction in which the force acts. From this follows the principle 
of the independence of motions, that when two or more forces i&ct upon 
a body at the same time, each produces exactly the same effect as 
though it acted alone, whether the body be originally at rest or in 
motion. Thus, if a person throws a ball due north from the roof of a 
house, while the wind is blowing from the west, the effect of the throw 
in the northerly direction will be exactly the same as it would if the 
air were quiet, while the distance that the ball is carried to the east 
will be equal to the distance that it would travel in the same time if 
it were under the influence of the wind alone, disregarding, of course, 
any unequal frictional resistances of the air. Moreover, as the ball 
leaves the hand, it will gradually drop to the earth under the influence 
of gravity, and it will take precisely as long for it to reach the grround 
as it would if it had been simply dropped from the edge of the roof. 
That is to say, the effect of the force of gravity is exactly the same as 
though it acted alone; each motion goes on independently, although 
the position of the ball at any time depends upon the action of all the 
forces acting. 

Law III. We have seen, under the subject of moments, how the 
supports of a beam react with a force equal to the downward pressure 
of the beam. There are many other evident illustrations of this law. 
A ton weight hanging on a crane hook exerts a downward pull of 2,000 
pounds, and the reaction of the hook and chain is also 2,000 pounds. 
When a horse pulls a cart there is the reaction of the load. In Jump- 
ing from a boat the reaction shoves the boat away from the shore. 
A man cannot "lift himself by his boot straps," because the downward 
push, or reaction, is equal to the upward pull. 


is equal to the mean Telocity during that second, multiplied hy the 
time. The mean velocity is equal to the sum of the reloclties at the 
beginning and end, dlTlded by the two. Hence, by the aid of the table 
above, we may make out another table showing the distance passed 
through in each second. Since the time is one second, or unity, the 
multiplication by this factor may be omitted. 


During Ist second, space = 16 

32 + 64 

During 2nd second, spaces = 48 


64 + 96 

During 3rd second, space = = 80 


96 4- 128 

During 4th second, space = = 112 


128 + 160 

During 5th second, space = = 144 


It will be observed that 48 = 3 X 16, or three times the space passed 
through in the first second. Also, 80 = 5x16; 112 = 7X16; and 
144 = 9 X 16. From this we conclude that the spaces traversed during 
each succeeding second are proportional to the odd numbers 1, 8, 6, 7, 
9, 11, etc., which is a useful fact to remember. 

We have seen that a body falls 16 feet the first second, 48 feet the 
second, 80 feet the third, and so on. In two seconds, therefore, it falls 
16 + 48 = 64 feet; in three seconds, 16 + 48 + 80 = 144 feet, and so 
on. But 64 = 16x4, or 16 X 2», and 144 = 16x9, or 16x8*, the 
2 and 3 in each case being the number of seconds required for a body 
to fall 64 to 144 feet, respectively. And, in general, the space that a 
body will fall in a given time is equal to 16 multiplied by the square of 
the number of seconds. Hence, 

At the end of 2nd space = 16 + 48 = 64 = 16 x 2*. 

At the end of 3rd space = 16 + 48 + 80 = 144 = 16 X 3*. 

At the end of 4th space = 16 + 48 + 80 + 112 = 256 = 16 X 4*. 

At the end of 5th space = 16 + 48 + 80 + 112 + 144 = 400= 16 X 5*. 

The factor 16 that has been used is one-half of 32, the acceleration 
due to gravity, or % g. Hence, to find the total space for any time, 
multiply the square of that time in seconds by ^^ g. Therefore, 

fc = ^(7f«. (11) 

Formulas 10 and 11 are the fundamental formulas for falling bodies. 
By combining them algebraically, we may obtain as an expression for 

vsaVTJS (12) 

From 10 and 12 may also be derived 

V VTJTS \ 2h 
^=~= = J (18) 

g g >i g 


Center of Oscillation 

The center of oscillation of a pendulum is tkat point which vibrates 
in the same time that it would if disconnected from all remaining 
particles. From Law II it is clear that the upper part of a pendulum 
tends to vibrate faster than the lower part, and so hasten its motion, 
while the lower part tends to vibrate slower and thus retard the motion 
of the whole. Between these two limits is the center of oscillation, 
which has the average velocity of all the particles of the pendulum, 
and which is neither quickened nor retarded by them. It vibrates in 
the same time that it would if it were a particle swinging by a 
weightless cord, as in the simple pendulum. 

It may make It clearer to state that the center of oscillation and 
center of percussion of a body are at the same point Hold an iron bar 
in the hand and strike an anvil a sharp blow with the end of the bar; 
it will sting the hand. Strike the anvil again with that part of the 
bar which is near the hand, and the effect of the blow will again be 
felt. Now, at some point between these two a blow may be delivered 
and no jerk or sting will be experienced. That point is the center of 
percussion, which, as just mentioned, is the same as the center of 
oscillation. In the case of a bar of uniform cross-section, and sus- 
pended at one end, the center of oscillation lies at a distance of two- 
thirds of the length of the rod from the point of suspension. 

The Compound Pendulum 

In order to apply the three laws to a compound pendulum, it Is 
necessary to determine its length, which, according to the definition 
previously given, is the distance from its point of suspension to its 
center of oscillation. This done, it may be considered as a simple 
pendulum having the same length, for any simple pendulum of a given 
length will vibrate in the same time that a compound pendulum of the 
same length will vibrate. 

It is important, therefore, to be able to locate the center of oscillation. 
This may be done by trial. The point of suspension and center of 
oscillation of a pendulum are mutually controvertible. If, therefore, a 
pendulum be inverted and another point of suspension found about 
which It will vibrate in the same time as before, this point wiU be the 
position of the first center of oscillation, and its distance from the 
first point of suspension can be measured. 

« Time of Vibration 

The time of vibration of a pendulum is found by the formula 

t = 3.1416 1— (14) 


where t=time in seconds. 
I = length in feet. 
^ = acceleration due to gravity. 

In the vicinity of New York, for t = l, 1 = 39.1 inches, or the length 
of the seconds pendulum is 39.1 inches. 



Hence we may write in formula (15), giving 


Wv^ Wv* Wv* 

B = ^X = = (16) 

82.16 64.32 2o 

It will be shown, shortly, how this formula is obtained. 

Conservation of Energy 

Energy exists in various forms, such as mechanical, molecular, and 
chemical. It is stored in all kinds of fuel, and is made apparent by 
chemical reactions, by muscular effort, and by many other means. 
There is the potential energy of the electrical charge and the kinetic 
energy of the electrical current. Heat is a form of energy. In the 
present instance, we are concerned with these different kinds, other 
than mechanical, only in that the universal and important law of tlie 
conservation of energy embraces them all. This law states, first, that 
energy may be transformed directly or indirectly from any one form 
into any other form; and second, that, however energy may be trans- 
formed or dissipated, the total amount of energy must forever remain 
the same. Energy can neither be created nor destroyed. It simply 
exists, and the various processes by which it is utilized are simply 
means for transforming it from one form into another. The steam 
engine changes heat energy into mechanical energy, and the percussion 
of a bullet against a rock converts mechanical into heat energy and 
melts the bullet. A body Just at the point of falling from an elevation 
has a store of potential energy. As it falls it loses potential energy, 
but its velocity increases and its potential energy is gradually changed 
into kinetic energy. This will be illustrated by an example. 

Suppose a body weighing 100 pounds, a cannon ball, for example, to 
be so situated that it has no store of potential energy, and that it is 
shot vertically upwards with a velocity of 1,500 feet per second. From 
formula (16) we find its kinetic energy at the start to be 

100 X ( 1,500 )• 

E=z = 3,498,100 foot-pounds. 


This results from the potential, chemical energy of the gunpowder, 
part of which has gone to produce heat and sound. As the ball rises, 
it does work against gravity, and also overcomes the frictional resist- 
ance of the air, the latter generating heat. When the ball is two miles 
high, lis potential energy is equal to 100 X 2 X 5,280 = 1,056,000 foot- 
pounds, and neglecting the frictional loss, its remaining kinetic energy 
is 3,498,100 — 1,056,000 = 2,442,100 foot-pounds. At the highest point 
reached the kinetic energy is entirely spent and the ball has its great- 
est store of potential energy. Could this be gathered together with 
the energy required for producing the heat and sound, it would exactly 
equal the amount of energy originally produced by the powder. As 
the ball drops to the earth again, its potential is changed back to 
kinetic energy, and when it reaches the ground it has the same Teloeity, 


merely ft special case of the principle of the conferration of energf , 
and it can be used to find the force of the blow delivered by a hammer 
or a falling body. The work put in by the energy and weight of a 
hammer at the instant of striking equals the work done in comprew 
ing or penetrating the material operated upon, and is equal to the re- 
sistance offered by the material, multiplied by the amount of this 

It is clear that the resistance offered to the blow at any instant is 
equal to the force of the blow at that instant, and hence the work done 
equals the force of the blow multiplied by the amount of the penetra- 
tion. It appears from this, moreover, that the force of a blow varies 
with the degree of penetration. Thus, suppose the energy of the flnt 
blow of a pile driver to be 10,000 foot-pounds, the weight of the pile 
driver 200 pounds, and that the pile sinks into the ground a distance 
of two feet Before the ram is brought to rest it will have performed 
10,000 + 200 X 2 = 10,400 foot-pounds of work, and hence the average 
force acting is 5,200 pounds for 5,200 (the force acting) times 2 (the 
distance through which it acts) equals 10,400 (the foot-pounds of 
work delivered). At the second stroke, suppose the ram again de- 
livers 10,000 foot-pounds of energy, but that the pile sinks only one 
foot, then the work done will be 10,000 + 200 X 1 = 10,200 foot-pounds, 
and the average force acting will be 10,200 pounds. 

When the force of a blow is calculated, the weight of the falling 
body should always be added to the energy due to the fall. If W== 
weight of falling body, i; = its velocity In feet per second, and cfss 
distance, in feet, the object struck is moved, then 

force of blow = \- W. 






Third Edition 


Principles of Punch and Die Work» by E. R. Markham 3 

Suggestions for the Making and Use of Dies - - 31 

Examples of Dies and Punches, by F. E. Shailor - 41 

Copyright. 1911, Tbe Indattrial Preu, Publlshen of Machinbbt, 
49-55 Lafayette Street. New York aty 



A third method consists in making a shoe having the back of the 
slot planed at the angle mentioned, while the front wall is made 
square with the bottom, the die being held with setscrews, as shown in 
Fig. 4. If this form is used, care must be exercised when laying out 
the screw holes, so that they do not come in line with the screws in the 
bolster when the shoe is in its proper place; and, again, the screws 
must not press on any portion of the die immediately in line with the 
opening, or it will be closed somewhat when pressure is applied to the 
screws. Fig. 4 shows the screws pressing on the solid portion of the die. 

b ^T=^h 







-I 1 1 

I ,1 M 




[I Shoe \\, 

n ni 



Fig. 2 
FigB. 1 to 4. Various MothodB of Holding Work 


Dies which are fastened in bolsters Without using a shoe must have 
their sides machined at an angle, as in Fig. 1, to prevent them lifting 
from the strain incident to removing the punch when it has pierced 
the stock. The angle should be from 10 degrees to 15 degrees, some 
mechanics claiming best results with 20 degrees. The latter, however, 
seems greater than there is any necessity for on ordinary work. 

Kind of Steel Used for Die Work 

For most work the stock used in making punches and dies should 
be a good quality of tool steel. A die that has cost from 5 dollars to 
100 dollars for labor is as liable to crack when hardening as though 


follow the edgea of the pattern, and the figure traced will be larg«r 
than desired. After the face has been made smooth bj plantng, grind- 
Ing or filing, the surface may be coated with blue vitriol solution, 
or It mar be heated until It assumea a distinct straw or blue color, 
and the outline of the piece to be punched laid out. 

K the die Is what la known as a solid die, that Is, made from one 
piece of stock, it may be laid off and prick-punched as In Fig. 6, after 
which boles may be drilled, leaving the face of the die as In Fig. 7, 

after which the core may be removed. When drilling for the opening, 
first drill any portions which are to be left circular or semi-circular 
In shape. These are then reamed from the opposite side with a taper 
reamer that will give the desired amount of clearance. When drilling 
to remove the core mentioned, some tool-makers use drills of sizes 
that break Into the next hole. After drilling all way round, the core 
drops out of Its own accord. If this method is adopted, best results 
follow the use of the straight-fluted drill. Fig. 9. Others drill -wVA 
drills of the size of the pilot of a counterbore, and after drllllns all 
the holes, the counterbore Is run through. Of course. It is understood 


Wben a mllllnc machine with a slotting attachment, Pig. IT, li used, 
abarp corners mar be cut to the line, as mar certain Irregular sur- 

faces which could not be shaped with milling cutters. Of course. It 
would be necessar? to have cutting tools of the proper shape to ma- 


chine the forms mentioned, the advisability of making which would 
depend on whether it would be cheaper to make the necessary tools 
and to do the machining, or file to the desired shape. A fixture known 
as a die shaper, whose action resembles the slotting device described 
above, is made to attach to a milling machine and works the same 
as the other attachment. 

In order to gage the angle of clearance it is advisable to have angle 
gages. Several of these may be made and kept in the tool chest and 
should be of the more common angles used. They may be of the 
form shown in Fig. 16, with the angle stamped on the heavier portion. 

Shear of Punches and Dies 

The cutting faces of dies are given shear for the same reason that 
the teeth of milling machine cutters are cut helical or spiral. The 
shear makes it possible to cut the blank from the sheet with less 
expenditure of power; it also reduces the strain on the die and punch. 
While it is customary to shear the face of the die when possible, 
there are instances when it is advisable to leave the face of the die 


Fl|f. 18. A Piece of Work for 

which the Punch Should be 

Provided with Shear 


Mmthtmtrgj X T. 

Fig. 19. A Case where the Shear should be 

on the Die 

fiat and shear the punch. The shear is given to the punch when the 
stock around the hole is the desired product and the stock removed is 
scrap, as in Fig. 18. The face of the die is sheared when the portion 
pressed through the die is the product, as at a a in Fig. 19, which also 
illustrates the shear of the die. 

The amount of shear necessary to give a die to obtain best results 
depends a great deal on the thickness of the stock to be punched, and 
also on the length of the piece to be removed, and on the power of 
the press. The shear of a die usually commoncos at the center and 
extends toward each end, as in Fig. 19, the punch being left flat on 
its face. When the punch descends, the cut commences at the highest 
point of the die, which is in the center, and continues toward each 
end. The portion at the center will have been removed from the stock 
before the cut has progressed very far toward the ends, and in this 
manner the cut is distributed over the length of the piece, reducing 
the strain on the press and tools. 

The diemaker, if he works to drawings furnished him by the drafts- 
man, makes the thickness of die and length of punch to corrospond 
with dimensions. However, it is customary in shops whore few dies 



are made and no draftsman is employed, to give the diemaker or 
toolmaker an idea ot the shape and dimensions wanted, or possibly a 
templet, and he is required to go ahead and "work out his own salva- 
tion.*' In such cases the workman must first find the dimensions of 
the press to be used, the distance from the bed to the ram, the length 
of stroke of the ram, the amount the ram may be adjusted, the thick- 
ness of the bolster, and particulars about any shoes that are to be 
used. These things should be carefully set down and kept where the 
workman may have access to them at any time. If there are several 
presses, each should be marked and the dimensions of each carefully 
recorded, according to the work of the individual machine. If this 
precaution is followed and the dimensions taken into consideration 
when machining the die and punch, there need be none of the trouble 
sometimes experienced, such as a die too thick or a punch too long, 
or the reverse, for the press in which they are to be used. 

Stripping the Stock 

When articles are punched from sheet stock, or in fact from any 
stock where the scrap is around the punch, the stock will be carried 


Tig. 20. ExAmple of Strlppintr Plate 

upward when the punch ascends, unless some device is furnished to 
prevent its doing so. Fig. 20 shows an arrangement a called a strip- 
per, or stripping plate, the opening in this being a trifle larger than 
the punch. The stripper plate must be securely fastened to the die, 
or the die holder, and must be stiff enough to prevent its springing 
when in use. Between the stripper and the die (at h) is a guide 
against which the stock being operate! on rests, and which determines 
the amount of scrap at the back edge of the sheet. This guide is 
made of a thickness that insures the space between the die and 
stripper being somewhat greater than the thickness of the stock uaed; 
in fact, the space must be sufficient to allow the stock to move along 



shown In Fig. 24. This method is open to the objection that the wire 
must be removed from the templet when it is used in laying out the 
punch, as it is necessary, when the templet differs in shape on two 
edges, to lay opposite sides of the templet against punch and die. 

Sectional Dies 

Dies are many times made in two or more sections in order to facili- 
tate the operation of working the opening to shape. In other cases 
the die, if solid, would be so large as to render it well-nigh impossible 
to harden it in a shop with only the usual facilities for doing work 
of this class. And then again if it should go out of shape in harden- 
ing, it would be a difficult task to remedy the defect. If made in sec- 
tions, as shown in Fig. 25, it would be possible to peen or grind to 
the original shape with little trouble. 

A die of the design shown in Fig. 26 may be made sectional be- 
cause it is much easier and cheaper to make than if solid. The sec- 




I I 


I ' 


I I 

Fig. 26. Sectional Die held by Screws 





— ' 

• o 

Mac/ttncry, A'. J', 

Figr. 26 Sectional Die Located by Taper Pins 

tions are held in their proper location by dowel pins. They are held 
together by the shoe which secures them in the press. If the die is 
comparatively small, the circular shapes at each end and center are 
produced by first drilling, and then reaming from the back, with a 
reamer of the proper angle. The sections may be separated and the 
balance of the stock removed in a shaper, planer or milling machine. 
When this stock is removed the die may bo held at the proper angle 
to produce the desired clearance. After machining as close as possi- 
ble, the surfaces may be finished with a file and scraper. 

When the opening has been finished to the templet, the top may be 
giren the proper shear. In order to facilitate the operation of grind- 
ing when the die is dull, the stock may be removed, as in Fig. 27, leav- 
ing about ^ inch on each side of the opening at the narrowest portion. 



There are certain forms of dies where It is not feasible to cut awaj a 
portion of the top, as shown, but where it can be done it saves much 
time when grinding. 

Correcting Mletakee Made in Dies 

Should the workman, through misunderstanding or carelessness, 
make the opening too large at any point, he should not attempt to 



MmMmgrjft K, Tt 
FI9. 27. Method of Cutttnff aw*y the Top of Die to Facilitate Orlnding 

peen the stock cold, as is sometimes done, for while it is possible 
to do this and then finish the surfaces in such a manner that it will 
be scarcely noticeable, the stock directly below where the peenlng took 
place will almost surely crack during the life of the die. 

Should the mistake referred to occur, heat the die to a forging heat, 
when the stock may be set in without injury to the steel. When set- 

Flfr. 28. CloaAnff up a Die which la too Large 

ting in, a blacksmith's fulling tool may be used, this placed on the 
face of the die and struck with a sledge, as in Fig. 28. If there la 
objection to disfiguring the top surface of the die, this method can, of 
course, not be used, but if the top is to be cut away, as shown in 
Fig. 27, the depression made by the fulling tool would be entirely cut 
away. It is never good practice to bend, set in, or otherwise alter the 
form of steel when cold, if it is to be hardened, as such attempts 
nearly always end in a manner entirely unsatisfactory. 


B«working Worn Dies 

When a die becomes worn so that the opening Is too large, or the iap 
edge of the walls of the Dpeniag are worn so that the die Is "bell mns- 
lied," it may be heated to a forging heat, set In with a fulling tool, or 
a punch of the desired shape, after which tt is reheated to a low rod 
and annealed. After annealing tt Is reworked to size. This rework- 
ing, care and Judgment being used, gives excellent results, and effects 
a considerable saving, as otherwise It would be necessarr to make new 
dies, while the die may be reworked at a traction of the expense of a 
new one. 

When making a sectional die, tt Is possible in case the opening Is a 
trifle too large, to work a little stock oft the faces that come together, 
provided the outer edges have not been planed to fit the holder; also. 

FlH. 29. ArrBjiBoment of OH Cooling Balh 

if It is allowable, these surfaces ma; be cut away the desired amount, 
and a strip of stock of the proper thickness placed between the die 
and bolder. ConslderlDg the liability of a mistake taking place when 
the beginner is doing work of this kind, it Is, generally speaking, 
advisable to leave the flttlng of the die to the holder until the opening 
has been worked to sls^.e. 

HardentnK Dies 

There is probably no one article tlie hardener is called on to harden 
that he dreads any more than a die. It he succeeds in bringing it 
out of the bath without a crack, he gives the credit to "luck"; and 
1( it cracks, it Is almost what ke was looking for. This is an unfor- 
tunate condition, as there is no need of losing dies in the operation of 
hardening. Of course. If a piece of imperfect steel Is used. It la almost 
sure to go to pieces In the bath; but if the steel is of the proper 
quality and in good condition, there need be no trouble when hard- 

When handling work so diversified tn character as the class under 
consideration, the operator should not assume that It Is i 



adopt any set method which is not to be deviated from, as there la no 
one class of work that calls for a greater exercise of skill and common 
sense than the proper hardening of punch-press dies, unless it be the 
hardening of drop-forging dies. For most dies of this character, how- 
ever, and especially for those complicated in form, and which mnst 
retain as nearly as possible exact measurements, there is no method 
that will give the satisfaction derived from the method known as 


When pack-hardening such pieces, best results are derived from the 
use of a bath of raw linseed oil of the type shown in Fig. 29, In 
which the oil Is kept from heating by being pumped through a coll of 








I - 





i- yk:^&^^:}^W4;:A.v^mm'm:imm 

Flff. 30. Dipping the Work In the Bath 

pipe in a tank of water, and then forced into the bath and through the 
opening as shown. If such a bath is not at hand, good results can be 
obtained where the oil is not agitated but the die is swung back and 
forth and moved up and down somewhat in the oil. If many dies are 
to be hardened this way, however, it is necessary to have a bath of 
generous proportions, or else several smaller baths, as it would not 
do to use the oil after it becomes hot, although oil that is heated some- 
what will conduct the heat from steel more rapidly than would be 
supposed, and is better adapted for hardening than if it is extremely 

Oeneral Directions for Hardening 

The secret of success in hardening dies by the ordinary method 
consists in getting as nearly as possible a uniform heat To accom- 
plish this the die cannot be heated very rapidly, as the edges and 
lighter portions would heat more rapidly than the balance of the 
piece. Unequal contraction, when quenching in the bath, follows on- 


even heating, and unequal contraction causes the die to crack. High 
heats cause cracks in steel. Then, again, high heats render the steel 
weak, and as a consequence it cannot stand the strain incident to 
contraction of one portion of the steel when another portion is hard» 
and consequently rigid and unyielding. Steel is the strongest when 
hardened at the proper temperature, known as the refining heat. 

Cold baths are a source of endless troubles when hardening dies. 
They will not make the steel any harder than one that is heated to a 
temperature of 60 or 70 degrees, or even warmer than this, but they 
will cause the die to spring or crack where the warmer bath would 
give excellent results. A bath of brine is to be preferred to one of 
water for this class of work, the brine being heated to the temperature 
mentioned above. 

Have the bath of generous proportions. When the die is properly 
heated, lower it into the bath as shown in Fig. 30, moving it slowly 
back and forth to the positions shown, which causes the liquid to cir- 
culate through the openings, thus insuring the walls of the opening 
hardening in a satisfactory manner. Then again, moving back and 
forth brings both surfaces of the piece in contact with the liquid, 
causing them to harden uniformly, and preventing an undue amount 
of "humping." as would be the case if one side hardened more rapidly 
than the other. The workman must, of course, exercise common sense 
when doing this class of work. If he were to swing a die containing 
sharp corners, intricate shapes, and fine projections ' as rapidly in the 
bath as it would be safe to do were the opening round or of an oval 
shape, it might prove disastrous to the die, as such a shape would give 
off its heat very rapidly, and as a result the fine projections and sharp 
corners would harden much quicker than the balance of the die; and 
as they continued to contract, the projections would fiy off, or the 
steel would crack in the corners. To avoid this, have the bath quite 
warm, move the die slowly, and as soon as the portions desired hard 
are in the proper condition, remove the die and plunge it in a bath of 
warm oil, where it may remain until cooled to the temperature of 
the oil. 

Most of the trouble experienced when hardening dies is occasioned 
by one of two causes — possibly both. The first cause is uneven heat- 
ing, the second, cold baths. 

The Punch 

The method of holding the punch depends on its shape and the style 
of die, as well as on the holders at hand in the shop. If it can be 
made as in Fig. 34, with a shank to fit a holder which enters an 
opening provided in the lower end of the ram, it will be comparatively 
simple to make. At other times it will be necessary to attach several 
punches to a holder, as in Fig. 31. When these punches can be 
attached to the holder by means of round shanks it will be found a 
satisfactory method. For many forms of punches, however, this would 
not answer, it being found necessary to attach them by screws, dowel 
pins being provided to keep them in position, as in Fig. 32 at a. 
Then, again, it is sometimes thought advisable to use a fixture for 



holding tbe punctieB. hRTlng a doT«-talled Blot cut In the fftee U 1b 
Fig. 33. the punches having a tongue which Ifl fitted In the sloL The 
punches are secureir held by means of eetscrewa. Aa the opening In 
tbe lower end ot the ram to receive the punch holder ol small pr csi ea 
Is ordinarily sauare, tbe holder Is made of a shape that fits tbe opea- 
Ing, tbe hole to receive tbe punch being round. At times tbe holder !■ 

I \ ^ugO 

FlSS. ai, Sa ksd 3S. Vu 

split as In Fig. 85. When pressure Is applied, the holder Is closed onto 
the shank of the punch, thus holding It securely. At other times the 
holder Is made without splitting, and a aetscrew placed In the lower 
end of the holder. Fig. SB. This setacrew, when screwed against the 
punch, holds It securely In place. 
It Is eostomarr to make tbe die, and harden It, and then make tbo 



punch and fit it to the die. After squaring the end of the punch that 
l8 to enter the die, the surface is colored with blue vitriol solution, 
or by heating it until a distinct brown or blue color is visible, after 
which the desired shape is marked on the face by scribing. If it is 
considered advisable to lay out the shape by means of the templet, it 
may be done; but if the templet is not of the same shape on its two 
edges, or the ends are different from one another, it will be necessary 
to place the opposite side against the punch, from that placed against 
the die when marking. However, it is the custom many times to 
mark the punch from the die. If the die is given shear, it is neces- 
sary to mark the punch before the face of the die is sheared. When 

FIG. 35 

FIG. 36 

FIG. 34 Maehlntrtjr.r, 

FifiTs. 34, 36 and 36. Punch and Punch-holders 

laying out several punches from a die which has a number of impres- 
sions, it is necessary to lay out the punch from the die. 

The surplus stock on the punch is removed by filing, chipping, mill- 
ing or planing, as the case may be, until it is but a trifle larger than 
the opening in the die. The end is then chamfered somewhat so that 
it enters the opening, and the punch is forced into the die a little way. 
It is then removed, the stock cut away, and the punch forced in again, 
this time somewhat further. This method is continued until the punch 
enters the die the required distance. It is then filed or scraped until 
the desired fit is obtained. When punch and die are to be used for 
punching paper, soft metals, or thin stock, the punch must fit nicely. 
If the stock is thick, or stiff, the punch may be somewhat looser. 



Pack-hardening makes an admirable method for hardening punchea 
for most work, but for piercing punches of the type in Fig. 37 It is 
not advocated, as the whole structure of the steel should be as nearly 
as possible alike. Such punches should be heated in a muffle furnace^ 
or in a tube in the open fire, turning occasionally to Insure uniform 
results, for not only can we heat a piece more uniformly if it is turned 
several times while heating, but a fact not generally known is that a 
cylindrical piece of steel heated in an ordinary fire without turning 

FIQ. 87 

FIQ. 88 

FIQ. 89 

Flffs. 87 and 38. Shapes Requiring Different Treatment in Hardening. 
Ft|r. 39. Clamp Used when Bcribingr Die Outline on Punch 

while heating will many times show softness on the side that was 
uppermost in the fire, no matter what care was taken when heating 
and dipping. If it is reheated with the opposite side uppermost, that 
will be found soft if tested after hardening, while the side that was 
soft before will be hard. The smaller the punch the more attention 
should be given to the condition of the bath. Luke warm brine is the 
best. Work the pnnch up and down and around well in the bath. 

Tempering Punches 

It is the custom of many mechanics to draw the temper of punches 
of the description shown in Fig. 37, to a full straw on the cutting end, 
but to have the temper lower further up the punch. Better results 
follow, however, if the punch is left of a uniform hardness its entire 
length of slender portion, as it is then of a uniform stiffness, and the 
liability of springing, especially when punching stiff or heavy stocky 
is reduced to a minimum. 

It is generally considered good practice to temper the punch so that 
it Is somewhat softer than the die; then, if from any accident the two 


come Id contact, the die will In all pro1>«t>IIIt7 cat tbe punch without 
much InJuiT to itaelf. There are exceptions to this, however. In many 
shops were large numbeia ot dies which are hardened are used. It la 
customaTT to hare the one which la the more dUhcnlt to maka the 
harder; M It will cat tb« other U the^ come In contact with each other. 
In order to hold the die and punch blank flrmljr together when 

Fl«. 40, Mnltlpla Dlft ud Btook Cut lii lM>ua 

marking the shape on the face of the punch, a ver; convenient Ibctun 
known as a die clamp, shown in Fig. 39, Is used. When the two are 
secured bj means ot this clamp. It Is possible to move them around 
80 as to set at the various portions where we wish to scribe. 
Multiple Dies 
A reduction In the cost of manufacture is often made possible bj the 
use of multiple dieg, whereby two or more pieces are punched out at 
a time. In punching perforated steel work It Is no uncommon thing 



to see punches and dies in use where several hundred punches are 
working into one die. 

If an article, for example, of the form shown in the die in Fig. 40» 
were to be punched in lots of several thousand, the die should punch 
a number at a stroke. Such a die and the stock left are shown in 
Fig. 40, where the die is shown at A and the stock after the first 
punching at B. It will be noticed that the distance between the open- 
ings is considerable. This is necessary, as it would not be possible 
to place the openings in the die as close as they should be to econo- 






^ . 




PLAN OF DIE Jtm€kin*rpjr,r, 

Figs. 41 and 42. Gang Punch and Die 

mize stock, since there would not be stock enough between to insure 
the die sufficient strength to stand up when working. For this reason 
the openings are located as shown. After punching as shown at B, 
the stock is moved along the right distance for the intervening stock 
to be punched out, as at C. 

Gang Dies 

If it were desirable to punch a piece like that at a in Fig. 43, it 
would be possible to make a blanking die and punch which would pro- 
duce the blank of the right size and shape, but without the holes; 
then, by means of another die, with three punches working into it, we 
could punch the holes. It is apparent that such a method would be 
more expensive than one that made it possible to punch the holes and 
the piece at one passage of the stock across the die. This may be done 
by the use of a die of the description shown in Figs. 41, 42 and 48. 
When using this die the stock is placed against the guide and Jnst 
far enough to the left so that the large punch l> will trim the end. 
Then, when placed against the stop or gage pin c, bring the guide pins 
in end of punch b in line with the holes punched at the first stroke of 
the press at the time the end was trimmed. 



the stock back to its proper location; whereas If the tool-maker 
attempted to locate the stop exactly, any dirt or other foreign sub- 
stance getting between the end of the scrap and the stop would cause 

Bending Dies 

While it is possible, in certain cases, to bend articles during the 
operation of punching, it is usually necessary to make a separate oper- 
ation of bending. There are instances where bending fixtures which 
may be held in a bench vise, or attached to the bench, answer the 












W Xi 





Fig. 44. Qtaig Punch Arranged to Use Sheet Stock 

purpose as well and allow the work to be done more cheaply than if 
bending dies were used. But as a rule the die used in a press provides 
the more satisfactory method, and allows the work to be done at a 
fraction of the cost. 

It is sometimes possible to make the dies so that the various oper^ 
ations can be done in different portions of the same die block, the piece 
of work being changed from one portion to another in order as the 
various operations are gone through. At other times it is necessary to 
make several sets of bending dies, the number depending on the num- 
ber of operations necessary. When a "batch*' of work has been run 


If the die Is ot tbe lorm shown in Fig. 47, It is. of course, necessair 
to make the length a of the punch shower than tbe distance acroM 
the opening of the die. It must be somewhat ehorter on each end 
than the thickness of the stock being worked. If possible, the upper 
comers b & ot the die should be rounded somewhat, as the stock tfends 
BO much easier and with leas danger of mutilating the surface than 
when tbe corners are sharp. When bending thin ductile metal the 
comers need but tittle rounding. If the stock Is thick, or very stiff, ■ 
greater amount of rounding Is needed. 

While tbe form of bending die In Fig. 4G answers for ordinary work, 
there are Jobs where such a die would not insure a degree ol accuraer 
that would answer the purpose, and it will be found necessary to mak* 
one similar to Fig. 48, where a riser or pad a is provided, as shown. 

This Is forced upward by the spring t> and is gaged as to height by 
means of the washer c bearing against a shoulder, as shown. It will 
be observed that tbe eprlng gets Its bearing against the washer, which 
In turn bears against tbe shoulder of the riser as mentioned before. 
When making this die, tbe hole is drilled and rea;ned and tbe groove 
milled or planed for the riser, which is put In place sufficiently tight to 
hold It while the V-groovc is out, after which it may be relieved until 
It works freely. The spring b gets Its lower b.;aTlng on tbe die 
holder. If It Is considered advisable, a screw may be provided for tbe 
spring to rest on. By adjusting this screw, any desired tension may be 
given the spring, although, generally speaking, this is not necessary. 

When bending articles ot certain shapes it Is necessary to design the 
tools 80 that certain portions of tbe piece will be bent before other 
portlana. Should we attempt to make tbe tools solid and do tbe work 


punch ball-Bhaped rather than aa ahown In Fig. 60. The ball anawen 
well on wire work and allows ol the easy removal ot the loop. It 
Is sametlmea desirable to cloae the upper end of an article nearlj 
toxether, and If the stock used ie extremely stiff, aa bow springs made 
from a grade of tool or spring steel, it mar be necessary to heat the 

n^. fiO. EM* fbr Bnjdluv Bow SprlD^a 

bow, which has previously been bent, red hot, and flnlEb bend It by 
a special process. In the case of articles made from a mild grade of 
stock the whole bending process may be accompllehed In one operation 
by substituting a. mandrel, aa shown In Fig. 53. for the cylindrical 
portion of the punch. 


A great variety of work may be done by modifications of the meth- 
ods for bending shown. Where but a few pieces are to be bent It Is not 
advisable to go to the expense of coetly bending dies; but when the 
work is done In great quantities, they will produce work uniform In 
shape at a low cost. Blanking and bending dies are made which not 
only punch the article from the commercial sheet, but bend it to tha 
desired shape at the same operation. As a rule. It Is advisable to 



and polished to produce very smooth walls. This may be accom- 
plished by using a round revolving lap of the right size. The slot is 
then milled as shown. If the die is not intended for permanent use 
and the stock is comparatively soft or easily bent, it need not be hard- 

"- ' ■^V '"-" • 

■A :■// '■ /<'■■'.', 

■//■■.■/'/, 1 


Figf. 55, Making a Tension Washer 

ened. If, however, it is to be used right along, it must be hardened. 
This is best accomplished by pack-hardening, being sure that the 
heat is low. As when using this method the die is quenched in oil, 
there is little or no danger of its going out of shape. It is then drawn 


I I 




FIG. 56 

FIG. 57 M''c}.\n»Tif,tf.Y. 

Figs. 56 and 57. A Curllnff Die and Its Work 

to a full straw color. The punch is m&de with a V-shaped impression 
in its face, as shown. This may be flat in the bottom, as indicated, or 
left sharp, as desired. 

It is possible with presses and tools adapted to the work to form 
pieces to shapes that to one not familiar with this class of work would 
seem well-nigh impossible. 


either by turning a round sbank on tbem. or doTe-tslllng them Into the 
cmet Iron holder In the same manner as the die. 

In planing up the die-blank It Is well to remember to take a Tery 
slight cut from the bottom and a cut about twice as deep from the top. 

Fi«. BS r\a- ss 

This removes the decarbonized surface from the cutting face where li 
needs meet to be done, but leaves It on the bottom where the die maj 
remain soft Where there Is a scarcity of 10-degree parallels, two 
pieces of drill-rod between the Jaws of the vise may be arranged to 


give the correct angle, as shown In Fig, 6S. Quarter-Inch drill-rod Is the 
size to use when the jaws are 1 9/16 Inch high. Where Intricate 
shapes must be drilled out with small drills, the holes may be laid 
out a trifle close together, and the shank of an old drill of the same sIm 



and that is the tendency of the punch to lift up the end blank while 
cutting it oft and produce a badly beveled edge. But if this portion of 
the strip is securely held down by the clamping device on the die as 
shown, the punch will have the same effect on both sides of the blank, 
cutting it ofC squarely. The gage and stripper held down by the cap- 
screws can be made a better fit on the stock than ordinarily, because 
it is not necessary to lift it up past a stop pin fastened to the die 
to enable the operator to feed the strip. By inclining the press, 
allowing one blank to slide out when released by the clamp, and letting 
the punched one drop through, two complete blanks are produced at 
each stroke of the press, with almost no scrap. 

The extension punch and die in Fig. 67 is quite useful on work 
which Is commonly beyond the scope of the press, such as the sheet 


/ I I ' ■ ' »' I 'I !■ ri 



1 1 

I ! I i 



' ■ ' 

K r --n 
►11 -- -J 

Machinery, .V. 1'. 
Figr. oe. Die for PunchJntf without Waste the Pieces shown In Fig. 64 

iron box shown In Fig. 63. This forms the sides of a slate-bottomed 
switch cabinet used on the old Manhattan Railway cars when they 
were equipped with electricity. The operations on this box included 
the bending of the 2 by i^-inch strap iron in four places, forming the 
lap joint, and riveting same. The cut shows the punch and die 
(without necessary stops and gages) in position for bending the cor- 
ners. The front clamping plate is removed from the ram and a cast 
steel extension bolted in its place with the same bolts. The large 
hook bolt extending into the hole in the ram and drawn up by the 
nut outside, is required to support the extension during the strain of 
bending. To allow the stock to clear the front of the press when bent 
into shape, the distance A in Fig. 67 should be a little more than 
half the width of the strap iron to be bent, and to avoid fouling the 
flywheel, comer x in Fig. 63 should be the flrst one bent after the lap 


bas been formed, and tben. In rotation, cornere v. e and a. When rui^ 
nfng tbe press at its accustomed speed on this Job the ends of tbe bent 
piece moved rather too fast for comfort, and It was therefore neceuair 
to cut dovn tbe speed of the flyrheel bj Inserting resistance In tbe 
annatnre circuit of tbe motor whlcb drove tbe line shaft to which 
three of these presses were belted.* 

Uethod of Iiocatlng Stock in Dies 
When a Job will not warrant the expense of a subtle, tbe device 
shown In Fig. 68 will help wonderfully toward producing aecurat* 
punchlngs. To simplify the explanation, the die shown la to cut 
washers, the holes being eccentric with the outside. Tbe die Is laid out 
the same as any double die, but tbe stop pin a Is added, and as will 
be noted, tbe extension K does not come out of the die. It, however, 

one depends entirely on this stop pin, the result will not be satlsfao- 
tory, because, when tbe stock is pulled against tbe stop pin, the w«b 
between tbe blanked places will bend a trifle, especially If the stock la 
thin. Therefore the long pins H are added, and as thette long pilota 
or traveling dowels are well pointed, and are considerably longer than 
tbe punches, they of course enter the holes and force the stock back 
to Its proper location. The pilots nt two boles in the die, and they 
therefore act as dowels while the puncb is cutting. Tbe pilots and tbe 
spring butts L keep the stock pressed drmiy against the gage side of 
tbe stripper, and the stock can vary 1/16 Incb. With ttala construction 
the operator is enabled to keep the press running constantly to the end 
of the strip. At each stroke the punch O cuts out the web and allows 
* H. J. Bachmaim, July, IMG. 


the stock to slide along to the next web, and there is absolutely no 
possibility of the stock jumping the stop. 

. As washer or small wheel dies are generally made to cut four or 
more blanks at one stroke, the following method of transferring the 
holes to stripper and punch-holder will be of benefit to some mechanics. 
If the punches are small, it is advisable to make the stripper, say, 
^ inch thick, and dowel it with four good-sized pins to the die. The 
holes through the stripper are bored to fit the punches nicely. This 
will act as a guide and prevents the punches from shearing. When 
the stripper is doweled to the die, we lay out the former with buttons or 
by other methods governed by the accuracy demanded, and each hole In 


' '1 







H ■ ' 'l 

, PUNCH HOLDER ■'■■'. 

■ \ ■ 'M 

...../. ■////./y /////. A/./. /..'.:::'. 




- -r- 


1 L 'JL 


I ^ - 

I ' ^ 

< >' t' 

l_ - , 

Fig. 68. Punch and Die with Guldo Pins 

turn is indicated and bored through the stripper and die. If the holes 
are so small that they will not readily admit boring to such length, 
the stripper may be bored and removed and the die then bored. The 
die must, of course, be fastened in such a manner that the stripper 
can be removed without loosening the die. If properly doweled, the 
punch-holder, stripper and die can be bored together, thus insuring 
perfect alignment of the punches and the die. 

Making an Irregular- shaped Die 

Fig. 69 shows a time-saver, as the die can be made easier and better 
because the parts can be ground to size instead of the die being filed 



out. Another advantage is that if the pieces warp in hardening they 
can be ground into shape again. The pieces M are shrunk on the sec- 
tions, holding them securely together. The holes N are drilled for 
clearance for the emery-wheel when grinding to size. The straps M 
are made a trifle shorter than the die over all, say 1/16 inch to the foot, 
and are heated red hot in the middle and placed in position while hot, 
and rapidly chilled. After these pieces are shrunk on, the dowels are 
transferred into the bolster. 

Another good kink when making irregularnshaped punches that are 
to cut thin stock is to make them of machine steel and case-harden 
them. Soft steel, case-hardened, does not change its form as much as 







® o 














Fiff. 69. Example of BuUt-up Die 

tool Steel, and even if the punch does change a trifle, the interior Is 
soft and can be readily forced back to position. The outside being 
hard, the punch will wear nearly as long as one made from tool steel, 
for practically the only wear on a punch is when passing through the 
stock. For thin brass the punch works well when made of tool steel 
and left soft, and when worn badly the punch can be peened on the face 
enough to upset, and then sheared into the die. When cutting a heavy 
blank, it is a good plan to grind the die so that the surface is quite 
rough, as the high spots then cut a trifle ahead of the low points. This 
will cause the die to run longer between grindings and is also easier 
on the press, while with a die that is ground perfectly smooth the 
entire cutting surfaces of punch and die meet simultaneously and the 
entire cutting surface of punch and die are placed under a tremendous 
strain. By grinding the die slightly lower on each end, thus producing 
a shearing cut, the die will last longer. 


A Kink in Hardening 

What will greatly reduce the chances of springins in hardenlag ef 
an irregularly shaped punch or die is to thoroughly anneal It after 
it has been machined nearly to size. This will, of course, not entl|«ly 
remoTe chances of accidents, as the prime cause of cracks and disUM^ 
tlon of work is to be found in the operator's way of Jt^ii^Hiig tiM 
piece to be hardened. An illustration of what takes place when hardk 
ening may be glTcn by referring to the die shown in Fig. 70. If we 
place the die in the fire, the points O will heat and expand Qoleiisr 
than the main body of the die, and there must be a sort of a '^uahtaiT 
effect between the points and the main body of the die. For this 
reason we heat "slowly and evenly." Now, when we dip the die in the 
bath, the points O immediately become chilled, and, of course, oontrtcfc 
while the main body is still red hot Assuming that the points httft 
become entirely cooled, there must be a line that separates the part 









JViiewvnap|ff SfmMm 

Fiff. 70. Die of Irreffular Shape Subjected to Heavy Btratns tn "^■^fif'^g 

that has been cooled off from the red-hot part. It must follow that 
when the main body begins to contract there is a powerful strain at 
the line that separates the parts contracting at different times. For 
this reason the die should be removed when quite warm; this allowa . 
the heat to run out into the points and the contraction will be aMve 
even. If allowed to cool in the bath there is apt to be a crack at D. 
Polish the die to draw the temper, and do not depend on settlBg 
an even temper by drawing the die when it is dirty, as one part may 
draw faster than another. 

Doweling Hardened Parts 

When making pieces such as sections of a built-up die, or any piaoe 
having dowel holes, it invariably happens that the dowel holes do not 
line up after hardening. One way to overcome this trouble Is to tap 
the dowel holes a trifle larger than the dowels to be need, and after 
the piece is hardened, screw in soft plugs and file them off flosll wUk 

•i . 



the work; when the piece is screwed in its proper place, the dowel 
holes are drilled and reamed through the soft screw bushings. This 
will save a great deal of unsatisfactory lapping.* 

Construction of Dies to Prevent Breakage in Hardening 

Another method of preventing breakage in hardening of dies with 
small projecting tongues, as shown in Fig. 70, is to construct the die 
in the manner outlined below. The die is first filed or machined in the 
regular way, with the exception that the two tongues are left out 
In line with the center of the tongues and at a certain distance from 
the cutting edge, holes are drilled larger than the width of the tongues. 
These are taper reamed from the top with a standard taper reamer. 
A slot is then cut from the holes into the die the same size as the 

Flff. 71. Method of Maldnir Dies to Prevent Bre«kage In Hardening 

tongue, when the die would look as shown in Fig. 71. We now make 
two pieces to fit in the holes, and extend out the required distance, 
making sure that they will be a drive fit after hardening. It is best 
if the pieces are 1/32 inch longer than the thickness of the die, so 
that they can be ground flush after being driven into place. While 
this may increase the cost of producing the die, yet, if from any acci- 
dent one or both tongues should be broken, they are easily replaced 
without the necessity of annealing the die.** 

Fig. 72 shows a very good method of making a die that is to contain 
a number of identically shaped teeth or points, such as dies for gear 
blanks, etc. While not being the most accurate method known, it is 
considered that for all work intrusted to a punch and die the method 
illustrated will be sufficiently accurate. A set of broaches are made, 
as shown in the cut, the number of steps being governed entirely by 
the length, or depth, of the teeth. The pilot fits the hole in the die, 
which is the diameter at the top of the teeth, and each step on the 
broach la 0.002 inch larger than the preceding step. The broaches 

• r. B. gtaaUor, March, 1007. 
•* K. L. Bom. Beptember, 1007. 



are made on oenten and necked in at Q to allow clearance for tlie 
chlpe. With a catter of the proper shape the teeth are then milled on 
the brpachee, naing the dlTiding head on the miller. After cnttlns 
the teeth on all of the broaches, the teeth on the punch ahonld be cat 


Fig. 7S. Broach ibr maldziff Dies fbr Gear Blaaka, etc 

at the same setting. The broach is then hardened and ground on tha 
faces as indicated. When used, each successive step is driven throngb 
the die until the last step is reached, and this should be driven throoi^ 
as many times as there are teeth in the broach, turning it one tooth 
each time. By doing this, whatever error may have been caused by 
hardening is overcome.* 

* F. E. BbaUor, January, 1904. 


die, le a novel and practical way la which this trouble la overcoaae. 
The stripper la ptaaed out 1/16 Inch wider than the stock and recessed 
to allow the sprlag guide N to slide freely when the stripper Is In 

position In the die. By glancing at the sketch the reader can readily 
see how the springs keep the stock pressing against the gage side at 
the stripper. The punch does not pertorm any work pertaining to 



the finished blank, but is used for cutting out the web in the stock in 
order to allow the strip to move along until the next web touches the 
stop pin. As the stop pin P does not come out of the stock it is there- 
fore impossible to "Jump" the stock and make a miscut, which would 
mean disaster to the drawing and forming punches. 

After setting up the die in the press, the punches of course descend 
five times before a single finished piece appears, but thereafter a fin- 
ished piece drops at each stroke of the press. The first punch, begin- 
ning at the left, indents the stock, and the punch is so adjusted that 
the face of the punch levels the stock. The second punch pierces the 
bottom of the indentation. The next punch draws the stock, and at 
the same time, forms the feather shown in the finished piece. The 
fourth is the forming punch and the last punch does the blanking. 

Fig. 74. Spadnff the Holes in the Die in Fig. 73 

Another interesting die is shown in Fig. 75. This die contains sev- 
eral novel features that will be found valuable to many engaged in 
die-making. As the sub-press die, the frames, and the power presses 
are of standard dimensions, it too frequently occurs that a die of a 
certain size requires specially made frames, and possibly a specially 
made press. The cut, Fig. 75, shows a practical way to construct a die 
that not only is a compact self-contained die, but that can be fitted to 
any style of press (of sufficient strength), having any length of stroke. 

This particular die was designed to produce the disk shown at A, 
Fig. 76, and previous to its introduction the disks were blanked out 
with a plain open die and then leveled by hand. The disks are of 
alnminum. 99 per cent pure, and, therefore* very soft, and as it is very 
essential that they should run as true as possible, great difficulty was 


•zperlenced In leveling them. The corrugating mats B B nere designed 
to level tbe disk and also to set. or Etlffea tbe metal, and ther proved 
a Buccess, for when the disks leave the die they are as Dearly level and 
true aa Ib possible to make, and so stltt that they can be handled quite 
roughly without injury. The disk was not corrugated Its entire sur- 
face owing to the fact that the mat would be obliged to act as tbe 
blanking punch, and If the corrugations extended clear to the edge of 
the mat, It could not be sharpened when dull. Therefore the rings 
CD were Introduced. The rlog C acts as the blanklag punch, and ring 
D acta as a leveling ring. The die is guided by means of two guide 
or pilot pins, E E. Fig. 76. and aa the gate of the press descends, the 
rings OD are the first to act on the stock to be punched, gripping it 
from above and below and holding the stock securely. Then, as the 
press continues downward, the rings settle back, still holding the stock, 
and the mats B B grip the blank. 

The rubber Bprlng, whlcb is one of the features of the design, exerts 
an Increasing pressure on the metal, pressing It Into the corrugatlona 

on the mata. The press is so adjusted that the ring C. nhlch la the 
blanking punch, cornea exactly flush with the die G. but does not enter. 
On tbe upward stroke of the press, the springs and rubber plate force 
the moving parts back to their original position, and force the diak out 
of the die. and the surplus stock oft the ring C. The rubber plate can 
be advantageously used In a small place where a very strong spring 
is required. The tension or spring effect la obtained by cutting holes 
B in tbe plate. Fig. 77. The more holes there are In the plate, the 
weaker the tension, as the holes permit the surrounding rubber to 
■QueeEe Into them. On the other hand If no holes were cut In the rubber 
plate, and the same fitted the recess la the die bored for It, there would 
be no more spring effect than If a metal plate were used. Rubber does 
not compress, but merely changes shape. Another novel feature ts 



that the guide plus are automat leal Ijr lubricated at each stroke of the 
press. The pins run Id the babbitt boxes / 1. Fig. 76, wtilcb have four 
grooves, J, cut the entire length of the babbitt and an oil chamber 
or reservoir K recessed near the top. A quantity of oil is placed In 
the bottom of the lx>x and as the pins descend they force the oil up 
through the grooves, J, into the reservoir, and as the pins ascend they 
form a partial vacuum at the bottom of the boi. which sucks the oil 
back to the bottom. 

Space win not allow describing the methods employed when making 
each part of the die, but It will suffice to say that with the exception 


FlB. TB. aids davaUon of Dl« aliowii In ShQoti In Fig. 7*. sad SempI* of Worfc 

of the mats, screws and holder, the parts were hardt^ned and accu* 
rately ground, making a smoothly running die. It might be well, 
however, to mention tbe method employed In making the square 
springs L. 

It Is well known what a difficult Job it Is to wind a heavy coil spring 
and have it a given diameter on the inside and outside, when flclshed. 
A large spring is generally made by heating wire red hot, and winding 
as many colls as possible before cooling, then reheating and winding 
more colls. The springs L L were made by gripping a piece of round 



tool steel In the lathe chuck, taming It to the glTen outside dlmmeter. 
The lathe was then geared to cut a coarse pitch thread and with a 
square thread tool, the thread was cut sufficiently deep. The inside 
of the spring-to-he was then hored out to the proper diameter, leaTing 
a spring the coils of which were evenly spaced, thereby causing each 
coil to perform equally its share of the work. With a wound spring 
the coils are yery seldom equally spaced, and when under pressure 
there is a greater strain on the coils furthest apart, causing the spring 
to either "set" or break at that point. 

JMMCri^ Prmit M.r, 

FtflT- T7. SpziBtf Rubber Plato 

After all parts of the die were completed, the die was assembled, 
leaving out the springs. The upper and lower parts were then brought 
together until the punches entered the dies, care being escercised that 
the upper and lower parts of the die were perfectly parallel with each 
other. The boxes II were then babbitted, first treating the guide pins 
with a light coating of flake graphite and oil to prevent the babbitt 
sticking to the pins. The writer considers that a large die of the aboiva 
description is tMT superior to the ordinary sub-press die, inasmuch as It 



is more compact, and also does away entirely with the cumbersome 
cast iron frame. 

Fig. 78 shows a die that is designed to take the place of the plain, 
open, double die. The ordinary double die is made with the stripper 
fastened to the die and planed out to allow the stock to slide 
through. The unsatisfactory results obtained when using a die of this 
style are well known. The greatest fault is that no two blanks are 
exactly alike, owing to the fact that the stock is wrinkled and does not 
lie level on the die. As the punches descend, they pierce the stock 
without leveling same, and as the blanks are afterward leveled, it is 
found that the pierced holes, being unevenly spaced, will not allow the 
blanks to interchange. By making the die, as shown in Fig. 78, with 
the stripper plate if fastened to the punch-holder and with a stifT coil 
spring at each corner, and so adjusted that the punches do not come 









Jndiutrial Prtm. S-F. 

"Fig. 78. Die with Stripper AttAched to Punch to Flatten Stock 

qui 10 flush with the face of the stripper, the above-mentioned trouble is 
nearly eliminated. On the downward stroke of the press the stripper M 
presses the stock firmly against the die, holding it level while the 
punches perform their work. The stock is guided by means of a small 
pin X at each end of the die. The stripper should not fit the punches; 
for if the operator should make a miscut, or should a piece of scrap 
punching get under the stripper, it would cause it to tilt and bring 
disaster to the small punches. 

Another valuable feature in this die is the manner in which the 
piercing punches are constructed. Ordinarily piercing punches are 
made solid, and If one breaks, it necessitates making a whole new 
punch or grinding the other punches down to the same length, greatly 



shortening the life of the die. The punches shown at O are designed 
to overcome this trouhle. A holder P is made and left soft, into which 
the punch (or rod) O is inserted, heing hacked up hy the screw Q and 
prevented from pulling out hy means of the screws R, Then, should 
one of the punches **flake" off, that same punch can he ground and 
then forced out hy means of the screw Q until it is at the same height 
as the others. This style of piercing punch greatly increases the life 
of a die. This die can be made either with or without the guide plna 
E E in Fig. 76. If made without the guide pins it is necessary to use 
the straps S to allow aligning the punches with the die when "setting 
up" in the press. The stripper is forced back and the straps inserted 
in the holes T T. After the die is "set up" and securely fastened, the 
straps are removed. 

All presses in which double dies are used should be provided with a 
separator, which is a plore of sheet metal fastened underneath the press 
to separate the scrap punch ings from the blanks. It is frequently 

U V 



X r 










\ m 


' '- — - --^- ■ . Z ^ ^I ZZ7. ~. - .. — .. ■/' 

Jndu9t^>t Pin* 

Fig. 70. Machine fbr BopamtJiiff UlHiikH ft-ora Stock Strips 

noticed that in factories where no separator is used, the cost of sorting 
the blanks from the scrap is in excess of the cost of blanking. A sub- 
press die loaves the blanks in a strip of stock. If the stock is over 
0.02 inch thick, considerable trouble is experienced in removing the 
blanks. Fig. 79 shows a means whereby the blanks are forced from 
the strip without marring them. V represents a soft rubber wheel, 
which is supported on ihe sides nearly to the edge by the washers y. 
The angle iron ir is provided with adjustable guides X and is recessed 
at y to receive bushings having different sized holes. A bushing la 
inserted in the angle iron having a hole somewhat larger than the 
blanks to be forced out. The guides X are then adjusted to allow the 
strip to slide freely. The angle iron is then raised by loosening the 
bolt Z until sufficient pressure is brought on the rubber wheel. The 
wheel heing power driven, all that is necessary is to place the end of 
a strip under the rubber wheel and it will roll the strip along, at the 
same time forcing out the blanks. 








Fourth Revised Edition 


Cutting Tools for Planer and Lathe, by W. J. Kaup - 3 

Boring Tools, by W. J. Kaup 11 

Forging Lathe Boring Tools, by J. F. Sallows - - 17 

Shape of Standard Shop Tools 20 

Cutting Speeds and Feeds for Lathe Tools - - - 29 

Straight and Circular Forming Tools, by Jos. M. 

Stabel and Geo. D. Hayikn - - - - 34 

GopFrldiU 1912. TIm iadintrial Prets, PnUitbcn of llACRncBSY. 
4»-B6 Late«tta StraeU New York City 



Another reason why a planer tool tendi to dlK toto tbe work li 
lIluBtrated In Fig. 3. Point A In ths sketch Is tbe lulcTum. In tha 
first sketch the tendency la for tbe tool to dig Into tbe work In the 
direction of the arrow. This Is not so serious as appears on the face 
of It, as planer tools are usually so stlB that they will aprlns but 
little, and any error that might occur In tbe ranstaing cut would b« 
eliminated in the finishing cut. What many mechanics take as an 
Indication of the sprinE of the tool Is really due to the chatter of the 
planer, since a rack and pinion planer will frequently chatter after It 
has become worn, while In a worm-drlTen planer the lost motion la 
all taken up at one end before beginning the cut, and the screw action 
does away with the chatter. To obviate any spring Into the work, the 
tool may be designed as In the aecond sketch. Fig. 3, where the deflec- . 
tfon due to the force of cut Is away from the work. 

The tool In F\g. 1 approachee the Ideal for a finishing tool, and 
gives the best finished surface of any used on planer or sliaper. It 
is made from a piece of ordinary tool steel and forged on the end to 









nnlflhlnff Tf>o 

the shape Indicated. It will be noticed that It has aide rake, and In- 
stead of being straight on the bottom, the line that comes in contact 
with the work Is a little rounding. 

The Outtlnff Edges of Lathe Tools 
We will now take up the subject of the cutting edges of some ol the 
many varieties of lathe tools, Fig. Q. Here are shown diamond point, 
round-nose, side, centering, thread-cutting and cuttlng-olT tools. We 
win first of all consider the diamond point tool, as it is by far more 
of a universal tool than any of tbe others. Before speaking of rmke. 
clearance, or the setting of the tool, attention should be called to tlu 
general form of the cutting edges and the Importance ot malntainins 
the same throughout the life of tbe tool. Fig. 7 will best Itlustrate 
this. The tool as shown at the left, with depth of cut. Is ground so 
that angle x shall not be less than 55 degrees. To the right Is a tool 
In which the angle has been changed by grinding on both sides of the 
point, only because the machinist clalma that he is in a hurrjr and 
must make time on hie work. But it will be seen that the length ot cot 
b Is much greater than the line of resistance a, showing loea In eS- 
rtency In the tool, and requiring more power to drive it after It had 


work. On the oUier end Is a leUI pencil attachment, the point bearing 
agftlnst tbe piece of paper Indicated, the paper travellas at the aame 
rata of speed as tbe work, only In the direction of tbe axis of th« 
work, kaj unevenneu In tbe surface of tbe work raises or lowers 
tbe point of tbe pencil, and as the ratio Is great (20 to 1), the varia- 
tion In tbe line Is marked. 

Bake and Clearanoe 
HeferrlnK to Pig. 2, we will take up tbe rake and clearance of lathe 
diamond point tools. Tbe angle of clearance, sometimes called tbe 
angle of relief, as Indicated here, Is about 7 degrees, and aometlmea 
runs to 10 degrees, more or less — enough for a safe working ancle. 
Really, tbe only reason for so much clearance Is to avoid rubblnc 
against the cut surface, thereby causing unnecessary frlctlonal resist- 
ance to the motion of the lathe. Our ettorts should lie directed toward 

TdsI, bkTlQC Sid* Mkk* 

finding the angle that will give tbe least force required for cutting, 
combined with endurance of the tool edge. 

Wblle tbe power required to cut Is Increased greatly by dullness ot 
the cutting edge, we must avoid the wood chisel edge, because time 
lost In constantly removing tbe tool for grinding purposes eats up the 
profit. In Fig. 9 are Illustrated two extreme cases — that on the left, 
too great top rake, and tbe other, without any. Tbe one will do good 
work for a tew minutes, provided tbe cut is not too heavy, but tbe 
wear of tbe edge la so great that tbe angle will soon become blunt, 
and It would be very much better to have no top rake at all. On the 
other hand, tbe cutting wedge, as I will call tbe tool shown at tbe 
right, is too blunt to do good, clean work, and from the position In 
which It Is set, tbe chip will come off nearly straight and In amaU 
pieces. The happy medium between the two Is indicated in Fig. 10. 

Side rake means the angle at which tbe top la ground either to the 
right or leK side. A tool ground for a traversing motion toward tbe 
left-hand, cannot be used with a motion toward the right. Therefore 
side rake Is designated right-hand or left-hand, the former belns that 
which givea a cutting edge on the right, and the latter, on the left 
sldft As the side rake Is Increased, tbe power to drive the tool along In 
its traversing direction becomea less, as it tends to screw lU way along. 


Now ft faw words ftbont grinding. The diamond point tool tbottU bo 
(round only on the top, and the angles on the aide* should never bo 
touchod, and th«re will be no dancer In sach a case of destrorlnc tho 
•oonomic value of the tool. Uany mechanics burn the catting edgw 
«t the tool in grinding, by simple carelessnesB, which makes the edg« 

softer than the metal It is supposted to cut. The references thus far 
have been confined entirely to the solid tools most commonly used. 
But there are many Improved tool-holders In use, designed tor seU* 
hardening steel which is not affected by burning in the hands of ln>- 
«ompetent mechanics, either In grinding or through lack of knowt 


edge of the proper cutting speeds. These holders support the Steel In 
snch a position as to give the proper front and side clearance, and the 
rake Is determined by the grinding. 

Speeds and Peeds 
Following is a table of finishing speeds and feeds for different 
metals for tools of ordinary tool steel. In roughlDE, the axiom Is slow 
speed and quick feed; in flnishlng, high speed and fine teed. From 
this table 25 per cent should be deducted for roughing speed, matlni 
18, 24, 28 and 83. Experiments on cutting tools made in the shops ot 
S. H. Smith, London, England, and verified by the author, show that 
machine steel requires from two to two and one-half times the ftmwt 



The centering tool should be ground like a twist drill and placed 
with its cutting point directly at the center of the work and uaed to 
obtain an accurate center for starting a drill. Much careleeaneaa Is 
exhibited in the use of the thread-cutting tool, not so much in grind- 
ing as in setting. It should be set so that the cutting edges are 
directly on the line of the lathe centers and, of course, at right angles 
to it The economical way to use this tool is to rough out the thread 
with a heavy cut, and then regrind the top surface until again sharps 
and then finish with a light cut. No matter how carefully a thread 
tool is used the sharp point will wear rapidly. 

Referring to Fig. 16, we come to the cutting-ofT tool, the last of the 
lathe tools shown in Fig. 5. The upper view shows the action of the 
tool and the two lower views indicate how good and poor results may 

llf . 18. T^pea of Boring Tools FI«. 10. Outdnff Aotfon of Bocteff Vooto 

be obtained through grinding. This tool has side clearance, right and 
left, and should be ground slightly concave on its top face. Its point 
should be on a level with the center of the work. 

' In Fig. 18 are indicated several of the more common types of boring 
tools. The vertical pressure on boring tools is very nearly constant 
(Fig. 19), and when the tool starts to cut, the depression or spring 
downward remains very nearly constant throughout its entire cut, 
and so does not vitally affect the accuracy. The tool wears as it 
advances, however, and this tends to produce a conical hole. While 
lathes are adjusted so that in no case they will bore a hole larger at 
the back than at the front, in making this adjustment, however, the 
tendency is to have the lathe so it will bore very slightly smaller at 
the back — another reason why bored holes are frequently a little 



In the previous chapter on cutting toola we confined ouraelTsi so- 
tlrely to one class, namely, planer and latbe tools, and the dlffennt 
conditions under vhich the beat results can be obtained from tbem. 
By best results Is understood the maximum amount ot good work with 
the minimum amount of energr expended — the Ideal for which emf 
good mechanic Is striving. It was attempted to make plain the car- 
dinal points for securing these results, such as proper top and side 
rake, clearance, rigid clamping, setting ot tool so that It will not spiinc 
Into the work, proper relation of cutting edge to center of work, etc 
All these combine to make the cutting edge the basis of economlo 
production, and economic production means not only least coat In 
manufacture, but a saving In wear and life of the machine. 

The subject ot cutting tools has purposely been divided Into two 
separate heads, as there Is a recognized distinction between Instda 
and outside turning. The rake and clearance of a tool for Inside turn- 
lug must be different from that used for outside turning, for two rea- 
sons: First, because of the contracted and peculiar conditions under 
which the boring tool works, and second, because of the spring of 
both tool and work — yery serious conditions met with In borlns which 
do not apply in outside turning. The spring of the work Is orercoaio 
In many cases by using a steadyrest to support one end of the work 
while the other end is held in the chuck, or else is clamped to tbs 
(aceplata and In addition la sometimes supported by the live center 

■ M*mi>RiT, Oclot>rr, imu. 



HoldiniT the Work tiirlitly Against the Center 

Fig. 20 may serve as a help to some who have found difficulty in 
keeping the work tight against the center. It shows the faceplate 
partly unscrewed. The lacing is made fast to a dog or carrier in that 
position, and the faceplate is then screwed up in place, thereby tighten* 
ing the thong. Now, unless great care and skill are combined in set- 
ting the steadyrest in position, the result will be failure, because^ in 
boring, the object is to get the bore concentric with the outside and it 
i»a very easy matter to defeat this object by careless setting of the 
rest. A suggestion as to the way of setting may here be in order. If 
it is a piece that has already been turned on the outside, the cent«r9 
may be used to good purpose. Keep the live center in the lathe spindle, 
screw the chuck in position and put the w*ork on centers, as for ordi- 
nary turning. Now bring the chuck Jaws down to the work and place 
the rest in position at the dead center end, the work all the while 
being still on centers. To remove the live center, the rest is then 
opened, the chuck, with the work in it, unscrewed, and the center 

■Jf—J H — l yt , N. r. 

Tig. 21. Comparison of PrlnciplAa of Outside and Inolde Tnmlnff 

removed. This method will insure fair accuracy, where it can be uaed» 
but the work when ready to bore should be tested with an indicator. 
If it is a rough piece of work that is to be set, support one end by the 
dead center, turn a true surface for the Jaws of the steadyrest and 
place the same in position while the work is still on the center. 

Difference Between Inside and Outside Turning 

Fig. 21 will prove that the same laws do not hold for both inside and 
outside turning. The circle on the left represents a cylinder to be 
turned; that on the right, a hole to be bored, with the tool in peti- 
tion. The lines a b and c d are drawn tangent with the work at the 
point where the cutting edge is in contact with the work, when taming 
and boring respectively. On the face of it, it would seem that one 
vertical line should answer for both conditions, but not so, for in 
turning we are enabled to set the cutting edge of the tool above the 
center of the work, hence changing the position of the lines and get- 
ting a finer cutting wedge. The angle A is the angle of the cutting 
wedge in turning, while B is the angle of the cutting wedge in boring: 
This is the best condition obtainable in boring. 



approximately the same position in the toolpost. It will, therefore, 
deflect as much in boring a short hole as in boring a long one, assum- 
ing the cutting edge to be in the same condition in each case. The 
longer the tool, the greater the deflection, for the tool is a cantileyer, 
the deflection of which is increased eight times when Its length la 
doubled. From this we can readily see how Important is this con- 
sideration of leverage, and how desirable it is to have the boring tool 
adjustable so that it need project from the point of support only so 
far as is necessary to bore the full depth of hole required. The 
mechanic should try to overcome the difficulty due to leverage by 
devising ways and means for making the tool adjustable. Many 
schemes are open to the thinking mechanic. 

Boring-tool Holders 

Fig. 23 will give an idea for a tool-holder and for different tools 
which are inexpensive and at the same time meet the above require- 



Flff. 23. Borlnir-tool Holder and Type of Inside Threading Tool 

ment. The holder gives at all times the greatest rigidity and allows 
the use of the largest size of tool possible for any particular work. 
It also enables the operator to vary the leverage to suit each particu- 
lar hole. 

The holder consists of a rectangular block of cast iron in which 
two holes are bored, one on each side of the center, and in a plane 
with the lathe center, and extremely close to the edges. After this, it 
is sawed in two through the center of the holes, the top forming the 
cap. The hole may be made any standard size: li/4, 1%, 1^, Into 
these holes are fitted sleeves or the drill rod itself, although the 
sleeves give wider range of size of boring tool for each holder, by 
having a number of sleeves with different standard size holes. The 
tool fits in either A or B of the sleeves. If the tool is to be used in A, 
a solid piece is inserted in B, so as to give a support for the cap to 
be clamped against. One end of the sleeve is knurled to allow for 
thumb and finger adjustment in raising and lowering the tool. Ordi- 
nary drill rod is used, filed down to a flat surface at the end, as 
shown. When heating for the tempering process, set over the filed end 



Boring' oat Tuba* 
In ituu>7 caaes It la desirable to bore holM of amall dUmetar but of 
KTMt length which extend through the entire length of a, tube, such 
tor eumple, aa core barrela tor rock drilling, where the tube la from 
10 to 14 feet long, and aa small In some caaea aa 3 inchea In dlametar. 
Fig. 25 will give an Idea ol the method bjr which auch boles majr ba 
bored with venr aatlafactorr results, and in Fig. 26 the boring bar 
la ahown in detail. The bar la made up of sectlona, aay 3 feet long, tha 
aectlona ao constructed that thej can be joined together into one bar. 
The work is supported In the lathe by two steady resta and la clamped 
to the carriage of the lathe by meana of wooden clamps, speclallr 
conatmcted to auft each lodlTldual case. The steadyreats are only 
used to guide and support the tube as the carriage advancea. carrying 

the tube with it. The end of the tube Is first bored to a depth of 
about 2 Inches with the ordinary boring tool, and made the requirad 
size. The bar Is then inserted until the cutter head reaches th« 
bored end of the tube which the guide ring on the outer end of the 
head should fit nicely. The tube la then clamped to the carriage, 
supported by the steadyrests, and the outer end of the bar la held 
by the lathe chuck. Allowance should be made for the tube to travel 
a distance equal to the entire length of one of the boring bar sectlona. 
When the tube has advanced this far, one of the sections of the bar la 
unscrewed and laid aside and the chuck engages the end of the next 
section, and ao the work proceeds until completed. It ahottld Iw 
observed that the face only of the tool should be used as a o 
edga. while th* outside acts simply aa a gulden 



Cold shuts, the starting point of the water cracks so often found 
In lathe tools, may be caused by heating the steel too quickly or too 
slowly. In heating too quickly, the center of the bar does not reach 
the same degree of heat as the outside of the bar, and consequently 
the outside part of the bar draws out under the hammer more freely 
than the center, thus causing a parting of the metal. This is the 
starting point for a water crack when hardening the tool. Heating a 
tool too slowly, and exposing it to the air either at the top or bot- 
tom, decarbonizes the steel, and a poor lathe tool may be the result 

FI9. 87. Bevel B«t 

When heating tool steel a heavy fire should be used, a good solid 
foundation of coke being laid in the bottom of the fire, and the steal 
should be well covered with coke. The smith must watch the stMl 
carefully, and not allow It to remain in the fire and "soak," as Is 
sometimes the case, especially if he has struck a position that is res^ 
ful, or has started an earnest conversation with his working mate. 

•MAcmixmn, Scptenbtr, 1907. 



WlMB forgUig a borlBs tool, a \mnX Mi dMmM bo uMd of tte tea 
ahowa la Fla. S7» baTlaa a rooad oonior at A. Aftor hoatlna tho ateoL 
4rtfo tlio Mt down, maktaa a *^!* as ibown at A, Fig. 18. Tte 
founded oomer forma tte Allot at tte tettooL Some nnltte noo a laifo 
top fnllor for makina tte ^r tat tte reeolt !■ a dnnuqr round oor- 





V1«.flO. Tool Bteak tvtih ddMlloMbto 

nor as stewn by tte dotted line B. If after drawing ont tte item of 
tte tool we turn over the lip on the end of an anvil teying sharp ear- 
ners* we shall get another sharp angle that may te the starting point 
for a water crack. (See A, Fig. 29.) The same also applies to angle 
B, lower view. Fig. 29. The anril used by the tool dresser steuld teve 


, s. r. 
Fl|r* so. Tool Blank wtth rorm of FQl«bi to b« Provided 

roond comers for about four inches from the square end on both 
sfdes. Then, when forging a tool that should teve fillets in place of 
tte sharp comers as shown at A and B, Fig. S0» the means are at hand 
for fbrming them. Nerer use a chisel on a lathe tool if it can te 

When about to lengthen out the stem on a boring tool, it is a eom- 
Don practice to heat the tool to a lemon heat, and with a chisel chop 



out a piece at A, Fig. 31, thus leaving the tool marred by chisel marks 
that caDDot be removed by hammering. Now, when the tool is used 
up to that part, it cracks every time it is put in the water. The proper 
way to lengthen a boring tool is as shown in Fig. 32. Drive the bevel 
set down as at A, then cut off the comer B, and draw out the stem 
to the proper length and size. If a boring tool has a fairly good lip 
and has to be lengthened in the stem, give the stem a half twist after 
lengthening, and the Job is completed. 

A common mistake a great many smiths make when tempering or 
hardening a boring tool is to heat the tool a little too hot, and dip 
the end into fresh water to a point just above the lip, and hold it still 


! A 


MacAitMry, If' f' 

Flff. 31. B*<1 Pr»ctic« In Lenffthoiilntf » Boftoff Tool Bttm 


FIf. 32. IUoommend«d PhmUoo Ibr Tiiigthwiing a Borlnir Tool 8tMn 

until it is cold. This is bad practice. In the first place the tool 
dresser should use salt water for hardening all kinds of tools, for the 
tools will harden at a much lower heat, and this will do away with 
cracking. In the second place the tool should be moved around in 
the water constantly until ready to be removed. 

An inside threading tool should be forged in the same way as the 
boring tool, except that, when trimming off the cutting part, it is 
shaped differently, being brought to a sharp point with clearance below. 
It should be tempered the same, however, as the boring tool, but will 
not stand to be quite so hard. 



The data relating to the proper shape of standard shop tools, and tt% 
tables of cutting speeds and feeds, given in this and the followliic 
chapter, are the results of experiments undertaken during a long 
period of years by Mr. Fred W. Taylor. The present chapter Is an 
abstract of that part of Mr. Taylor's work, "On the Art of Cutting 
Metals," which deals with the proper shape of tools. 

In Mr. Taylor's practical experience in managing shops, he found it 

no easy matter to maintain at all times an ample supply of cutting 

tools ready for immediate use by each machinist, treated and grouncl 

so as to be uniform in quality and shape; and the greater the yarlety 

in the shape and size of the tools, the greater became the difflcnlty 

of keeping always ready a sufficient supply of uniform tools. His 

whole experience, therefore, points to the necessity of adopting as 

small a number of standard shapes and sizes of tools as practicable. 

It is far better for a machine shop to err upon the side of having 

too little variety in the shape of its tools rather than on that of having 

too many shapes. 

Standard TooIb^ 

In the engravings Figs. 33 to 44, inclusive, are shown the shapes of 
the standard tools which Mr. Taylor adopted, and in Justification of 
his selection he states that these tools have been in practical use in 
several shops, both large and small, through a term of years, and are 
giving general, all-round satisfaction. It is a matter of interest also 
to note that in several instances changes were introduced in the de- 
sign of these tools at the request of some one foreman or superin- 
tendent, and after a trial on a large scale in the shop of the suggested 
improvements, tlie standards as illustrated here were again returned 
to. These shapes may be said, therefore, to have stood the test of 
extended practical use on a great variety of work. 

Blements Considered in Adopting Standard Tools 

These standard tools may be said to represent a compromise in which 
each one of the following elements has received most careful considera- 
tion, and has had its due influence in the design of the tool; and it 
can also be said that hardly a single element in the tools is such as 
would be adopted if no other element required consideration. The 
following, broadly speaking, are the four objects to be kept in mind 
in the design of a standard tool: 

a. The necessity of leaving the forging or casting to be cut with a 
true and sufllciently smooth surface; 

h. The removal of the metal in the shortest time; 

• Macbinsbt, March, 1907. 



Relatlye Importance of the Blements Affeotlnir the Outtinff Speed 

The cutting speed of a tool is directly dependent upon the followtns 
elements. The order in which the elements are given indicates their 
relative effect in modifying the cutting speed, and in order to compare 
them, we have given in each case figures which represent, broadly 
speaking, the ratio between the lower and higher limits of speed as 
affected by each element 

A. The quality of the metal which is to be cut, <.e., its hardness or 
other qualities which affect the cutting speed. Proportion is as 1 In 
the case of semi-hardened steel or chilled iron, to 100 in the case of 
very soft low-carbon steel. 

B. The chemical composition of the steel from which the toel is 
made, and the heat treatment of the tool. Proportion is as 1 in tools 
made from tempered carbon steel, to 7 in the best high-speed tools. 



Fig. 84. Tool tor Cuttixiff Medium and Soft steel 

C. The thickness of the shaving; or, the thickness of the spiral strip 
or band of metal which is to be removed by the tool, measured while 
the metal retains its original density; not the thickness of the actual 
shaving, the metal of which has become partly disintegrated. Pro- 
portion is as 1 with thickness of shaving 3/16 of an inch, to S 1/2 wiUi 
thickness of shaving 1/64 of an inch. 

D. The shape or contour of the cutting edge of the tool, chiefly be- 
cause of the eCTect which it has upon the thickness of the shaving. 
Proportion is as 1 in a thread tool, to 6 in a broad-nosed cutting tooL 

B, Whether a copious stream of water or other cooling medium is 
used on the tool. Proportion is as 1 for tool running dry, to 1.41 for 
tool cooled by a copious stream of water. 

F, The depth of the cut; or, one-half of the amount by which the 
forging or casting is being reduced in diameter in turning. Proportion 
is as 1 with ^rinch depth of cut, to 1.36 with %-inch depth of cut. 

G. The duration of the cut; i.e., the time which a tool must last 
under pressure of the shaving without being reground. Proportion fm 
as 1 when tool is to be ground every 1% hour, to 1.207 when tool Is to 
be ground every 20 minutes. 



Object of Having the Cuttinir Bd^e of Tools Curved 

A tool whose cutting edge forms a curved line of necessltj remoTea 
a shaylng which varies In Its thickness at all iMirts. The only type of 
tool which can remove a shaving of uniform thickness Is one with a 
straight-line cutting edge. The object In having the line of the catting 
edge of a roughing tool curved as that part of the cutting edge which 
does the finishing Is approached, Is to thin down the shaving at this 
point to such an extent as will Insure the finishing part of the tool 
remaining sharp and uninjured even though the main portion of the 
cutting edge may have been ruined through over-heating or from some 
other cause. 

Advantages and Disadvantages of Broad-nosed Tools 

Upon appreciating the Increase In the cutting speed obtained through 
thinning down the shaving as shown In the experiments with straight 
cutting edge tools, the tools shown In Figs. 45, 46 and 48 were made, 
and used on roughing work for years in the axle lathes of the Mldvale 
Steel Company. The gain In cutting speed of these standard broad* 

^-z— OLIARANCe •• 

'<«P BACK tLOPI •• 

8I0C tLOPC 14* 

•IOC ei.OPE 14*^ 


Flff. 37. Standard Tool 
for Wide Feeds 

Flff. 38. Tool used in most of 
the Taylor Bxperlments 

nosed tools over our standard round-nosed tools, shown In Figs. 37 
and 38, is in the ratio of 1.30 : 1. This general shape of tool continues 
to be extensively used, but it is subject to the disadvantage that It 
is likely to cause the work to chatter, and so leave a more or less 
Irregular finish. Were it not for this difficulty, added to the fact that 
the standard round-nosed tool has a greater all-round adaptability and 
•convenience, the tools illustrated in Figs. 45, 46 and 48 would undoubt- 
edly be the proper shapes for shop standards. 

Influence of Small Radius of Curvature on Chatter 

Since the thickness of the shaving is uniform with straight edge 
tools. It is evident that the period of high pressure will arrive at all 
points along the cutting edge of this tool at the same Instant and will 
be followed an instant later by a corresponding period of low pressure; 
and that when these periods of maximum and minimum pressure ap- 
proximately correspond to, or synchronize with the natural periods of 
vibration either In the forging, the tool, the tool support, or in any 
part of the driving mechanism of the machine, there will be a resultant 






i -, 















' 1 





*■ — -^ — * 


chatter in the work. On the other hand, in the case of tools with 
curved cutting edges, the thickness of the shaving varies at all points 
along the cutting edge. From this fact it is obvious that when the 
highest pressure corresponding to one thickness of shaving along a 
curved cutting edge is reached, the lowest pressure which corresponds 
to another thickness of shaving at another part of the cutting edge Is 
likely to occur at about the same time, and that therefore variations 
up and down in pressure at different parts of the curve will balance or 
compensate one for the other. It is evident, moreover, that at no one 
period of time can the wave of high pressure or low pressure extend 
along the whole length of the curved cutting edge. 

Relation Between Cost of Forging and Orindlng 

In adopting the general shape or conformation of a tool (we do not 
here refer to the curve of the cutting edge), the most important con- 
sideration is that of selecting a shape with which the largest amount 
of work can be done for the smallest combined coat of forging or dreti- 
ing and grinding, and the dressing is the much more expensive of these 
two operations. It is, therefore, of paramount importance to so design 
the tool that it can be ground : 

a. The greatest number of times with a single dressing; 

5. With the smallest cost each time it is ground. 

Modern high-speed tools when run at economical speeds are injured 
much more upon the lip surface than upon the clearance flank. There- 
fore, at each grinding a larger amount of metal must be ground away 
from the lip surface than from the clearance flank; and yet in many 
cases the clearance flank will be more or less injured (rubbed or 
scraped away) below the cutting edge, and it therefore becomes neces- 
sary, for maximum economy, in practical use, to grind roughing tools 
both upon their lip and their clearance surfaces. 

In many shops the practice still prevails of merely cutting a piece 
of the proper length from a bar of steel and grinding the curve or 
outline of the cutting edge at the same level as the top of the tool, 
as shown in Figs. 47 and 49. This entails the minimum cost for dress- 
ing, but makes the grinding very expensive, since the lip surface must 
be ground down into the solid bar of steel, thus bringing the corner of 
the grindstone or emery wheel at once into action and keeping It 
continually at work. This quickly rounds over the comer of the stone, 
and necessitates its frequent truing up, thus increasing the cost of 
grinding, both owing to the waste of the stone and the time required 
to keep it in order; and it also leaves the face of the grindstone high 
in the center most of the time, and unfit for accurate work. As far 
as possible, then, the shape of standard cutting tools should be such as 
to call for little or no grinding in which the comer of the emery wheel 
does much work. With the type of tool illustrated in Fig. 49, also, 
comparatively few grindings will make a deep depression in the body 
of the tool, as shown in the lower view of P^g. 50, and this depression 
will, of course, be greater the steeper the back slope of the lip surface 
of the tool. 






To avoid these difficulties, perhaps the larger number of well-man- 
aged machine shops in this country have adopted a type for dressing 
their tools in which the front of the tool is forged slightly aboye the 
leyel of the tool, as shown in the lower yiew of Fig. 47 and in the 
middle view of Pig. 60. This type of tool dressing is done in each of 
the following ways: 

A. By laying the tool on its side and slightly flattening its nose 
by striking it with a sledge, thus narrowivg the nose of the tool and 
at the same time raising it slightly above the level of the top of the 

B. By cutting off the clearance flank of the tool at a larger angle 
than is demanded for clearance, and then slightly turning up the 
cutting edge of the tool through sledging upon the clearance flank 
while the tool is held upon the edge of the anvil with its shank below 
the level of the anvil. 

The objection to both of these types is that the tools require redress- 
ing after being ground a comparatively small number of times, and 
that when redressed, in many cases the whole nose of the tool Is cut off 
and thrown away. This waste of metal, however, is of much less 
consequence than the frequency of dressing. With the first of these 
types of tool dressing the tendency is to make the nose of the tool too 
thin, that is, having too small a radius of curvature, and thus to fur- 
nish a tool which must be run at too slow a cutting speed. 

Length of Shanks of Cutting Tools* 

In choosing the proper lengths for cutting tools, we again find two 
conflicting considerations: 

A. It requires a certain very considerable length for the shank of 
the cutting tool in order to fasten or clamp it in its toolpost. When 
the tool becomes shorter than this minimum, it must be thrown away, 
thus wasting costly metal, particularly in the case of the modem high- 
speed tools. 

B. On the other hand, the longer the body of the tool, the more 
awkward and the slower become all of the operations in handling the 
tool, beginning with the dressing and followed by the grinding, stor- 
ing, handling in the tool-room, and setting and adjusting in the 

There Is no definite, clear-cut method of comparing the relative loss 
in handling long and heavy tools with that of the waste of the tool 
steel, so that the adoption of standard lengths for dressing tools of 
various sizes has been largely a matter of "rule of thumb" Judgment, 
and the length of tools which have been adopted, corresponding to dif- 
ferent sized bodies, is given in the table below. 

Let width of shank of tool = A, and length of tool = L; then L = 
14A + 4 inches. 

Size of Size of Size of 

Shank of Len^h of Shank of Lenj^h of Shank of Length of 

Tool, Tool, Tool, Tool, Tool, Tool, 

inches. inches. inches. inches. inches. inches. 

%x % 11 %xl% 16% m^x2% 26 

%xl 12% IxlV^ 18 l%x2% 28% 

%xUA 14% l%xl% 21% 2x3 32 

* MACBi2fEBT, April, 1907. 


i I i 



I ^ 



Almost every machlnlBt who Is engaged in tool work vlll turn nun* 
or less to do witb the making of ronnlsg tools. Tbeae mar be umA 
for shaping sheet metals, or for use under the drop hammer, or *■>!>• 
they may be employed In the lathe, planer, Bhaper, or milling macfalna. 
It la tlie object In the present chapter, however, to conSne ourselns 
to a description of the Btralght and circular forming tools that ara m 
onlversallr used on screw machines. For certain purposes these toda 
need not be or a very exact nature, while, again, they requlra graat 
accuracy In their construction when they are to he used lor tbe manu- 
facture of tntercbauKeable parts. As the old saying goes: "It Is eaaf 
enough to make one alike," but when It is necessary to make duplicate 
tools It la quite a dltBcuIt task. 

While there are numerous methods employed for making Uiese toOla. 

but little has ever been written In a nay which will enable the machin- 
ist to compute the distances, diameters, or angles so as to produce tha 
required dimensions on the finiahed work. II, for instance, a circular 
tool is to produce certain diameters on the work, and we transfer the 
exact ratio ot Itaese different diameters from the drawing to the form- ■ 
lug tool, we wil[ not be able to get the required dimensions when the 
cutting edge of the tool Is one-quarter ot an inch below the center. It 
we have to make a straight forming toot which. In the machine. Is to 
stand at an angle of 15 degrees, ne can, when It la not very wide, 
avail ourscives of the use ot a master forming tool. When, howerer. 
the tool Is very wide, so that the use of the master tool Ib unpractical, 
and It la necessary to mill or plane It to ahape, some computatloB la 
then necessary In order to make the ahape such that It will prodac« 
the required dimensions on the work when the tool is held at an angl* 
in the machine. 

Making StTBLlgbt Forming' Toole* 

We will Qrst consider a method ot making straight forming tools 
which has proved eailsfactory and will produce accurate results if 
* UiCBiNBBl, June, 1904. 



at the same angle with tbe perpendicular «a the tormlns tool !■ to 
•tand when placed In the screw machine, and It Is verr mmdIUI to 
observe this point If accurate results are desired. When the proper 
angle of the former has baen obtained, It Is secured In poaltloa by a 
wooden wedge tapped In between the cone and the frame of the milling 


machine', and the table is then rim ba<'k and forth until the tormlng 
tool 1b cut to the desired shape. 

Dae of Second Maater Former 

It an extra long forming tool Is required, aajr eight or nine lactaea 

In lengiii, and it la desired to prolong the life of the master fonner, 

we would then make use of a second master former, constructed aa 

previously described for the forming tool. This second master former 

Flc. fi4. llBklnv tba Formliv Toot from tha llaMar Pormar 

fits into a bolder, as shown In Fig. 55, and when it Is being fomud 
should be held at right angles with the bed of tne machine. It U 
then necesBarr to make a similar piece to be osed tor making tbe 
working formers. To avoid confusion we wUl call this first plectt 
No. 1 and the next piece to be made No. 2. This second pleoe must 
have the form of No. 1 transferred to it and tor Ihli purpose It la 



MaWng Oonoave Forming Tools in the Milling ICfteliiiie^ 

Pig. 58 illustrates a very interesting method of making a ooneate 
forming tool such as is used for backing off convex milltng cutters. 
This tool has, of course, the same shape for its entire depth so thai it 
may be ground and reground without changing its original form. 

In Fig. 58, B represents the tool which is held in the holder A at 
an angle of 76 degrees with the table of the milling machine, this 
giving to the tool the proper cutting clearance. The first thing to be 
done, after placing the tool in the holder, is to mill off the top of the 
tool so that it will be parallel with the table of the machine. A semi- 

Fig. 67. MeUiod of Holding 8«oond ICaster Former In Shaper 

circle of the desired radius is then drawn on the back of the tool, and 
with any cutter that is at hand, it is milled nearly to the mark, care 
being taken not to go below it. For finishing the cutter, a plug, C, is 
made, the end being hardened and ground in a surface grinder. This 
plug is held in a special holder, D, which fits the spindle of the milling 
machine, and when it is set so that its axis is perpendicular to the 
tool, the spindle of the machine is firmly locked. Some machines are 
now being built with proylsion for locking the spindle, but if not so 
made the same result may be accomplished by driving wedges undw 
the cone pulley. Now, by moving the platen of the machine backward 
and forward by hand, the plug can be made to cut a perfect semi-drcto 
in the tool. 

* Macbinbrt, December. 1903. 



It is good practice to plane a little below half of the diameter of 
the plug, thus allowing some stock to be ground off after the tool is 
hardened. In hardening, these tools usually come out very satisfac- 
torily, but, if any distortion takes place, it will be from the sides, and 
may be readily remedied by a little stoning. By using the concaye 
tool for a planing tool, as shown in the sketch at G, a convex tool may 
be formed, but in doing so care should be taken that both tools stand 
at an angle of 76 degrees with the bed of the machine. This shape 
of tool would be used for backing off a concave cutter. The descrip- 
tion of this method was contributed to Machineby, December, 1903» by 
J. J. Lynskey. 

Computing Dimensions for Forming Tools* 

The foregoing methods have all been based upon the duplication of 
the formers by mechanical means, but we will now consider other 
methods in which the dimensions of the formed tool are computed 
from the ratios of the different diameters on the work. We have 
already made it clear that an error will exist if we transfer to the 
tool the exact difterences in the various radii on the work, and it is 
to overcome this error that we subtract from the dimensions of the 
work such dlfTerences as are caused by the tool standing at an angle 
in the machine. 

As will be readily seen in the figure at the head of Table No. 1, the 
line a c is always longer than t c, and as a c must be equal to the differ- 
ence between two radii on the work, t c will consequently equal acX 
cosine of the angle at which the tool is to rest in the machine. Table 
No. 1 is arranged to facilitate the computation of the tool dimensions to 
give required dimensions on the work. In the first column is given the 
distance ac, or the actual cutting distance; and the second, third and 
fourth columns give corresponding distances & c when the tool is to 
stand at an angle of ten, fifteen or twenty degrees in the machine. 

To illustrate the use of this table we will take as an example the 
piece shown in Fig. 59, the respective diameters of which are 1.75 inch, 
0.75 inch and 1.25 inch. We will first reduce these diameters to thejjr. 
respective radii, which equal 0.875, 0.375 and 0.625. Now the diffeit" 
ence between the first and the second is 0.500, which would equal the 
actual cutting edge on the tool, or a c. Referring to our table we find 
in the first column our distance a c = 0.500, and if the tool is to set 
at an angle of 15 degrees we find our corresponding value for 5 c in 
the third column ; & c = 0.482965. In the same way we find our second 
step which, for a difPerence in radii of 0.25, equals 0.193186 + 0.048297 = 
0.241483. If we then plane our forming tool so that the st^iw will 
measure 0.4830 and 0.2415 respectively, when this tool is placed in the 
machine with the cutting face perfectly central with the work, and 
the front face at an angle of 15 degrees, the diameters tamed will 
correspond to those in the sketch. 

It often happens that an angle is to be turned upon the piece and 
this angle will naturally change when the tool is placed at an angle. 

* BCACBiKnT, June, 1904. 



TAble No. 2 has therefore been computed to give the angle that Is ta be 
made on the UkA for obtaining a required angle on the work. The 
angles glTen are measured from the center line of the piece or, what 
is the same thing, with the formed face of the tool. Thus In Fig. 61 
we have an angle of 45 degrees, and as the forming tool will rest at 
an angle of 15 degrees in the machine, we refer to the third column of 
TM>le No. 2, where we find 44 degrees as the proper angle for the tool, 
and if the tool is made to this angle it will cut the work to the 45 
degrees required. The angular difference, as will be seen, is the 

Wig. 50. Bz»mpl« of Work for which Forming Tool DlmmaMons are to bo Oompnfeod 

greatest at 45 degrees, from which it decreases at about the same 
rate toward asero and 90 degrees. 

Circular Forming Tools 

Circular forming tools are used in the same capacity as straight 
ones, and to make them accurately entails quite a little computation. 
Whenever a circular tool has two or more diameters a discrepancy 
will exist between the different diameters on the tool and on the 

OO m Badhig of fonnhig tooL 

OB ss Seoond rtdiiif of fonning tod. 

OA X Distanoe fronr centor to cuttiog tmob of tooL 

AB= ^OB*- OA» 

BC= ^{OC»-OA») ^{OB»~OA») 

Tig. eo. FonnnlAa ft>r OtrculAr Pormioff Tools 

work, if the cutting face is below the center of the tool. In Pig. €0 
are given the formulas necessary for calculating the diameters of 
circular forming tools, and Table No. 3 has been computed to show the 
discrepancies and to assist in determining the proper diameters of 
formed tools to give required diameters on the work. The first and 
second columns give the diameters and radii respectively of the formed 
tools, while the third column gives the distance from the vertical 


center lin« ot tlie tool to the cutting edge when tb« cuttinc face Is H 
Inch below the horliontnl center line. The fallowing three columM 
glre the constants tbat are to be need In computing the vnrloiu diUM- 
ten ot the forming tools when the cutting lace Is ^ inch below the 
horlxontal center line, as will be made clear in the example tollowliig. 
In the remalaing columns sre tabulated similar valuee as these, tor 
use when the cutting face of the tool la 3/16, 1/4. and 5/lS inch below 
the horizontal center line ot the tool. As there is no standard di» 
tance tor the location of the cutting face, the table has accordlttglr 
been prepared to correspond with such distances as are most eob 
monlr used. 

As an example illustrating the use ot these tables we will consider 
that we are to make a circular forming tool for the piece shown In 
Pig. 69, and tbat the largest diameter of the tool is to be 3 inches, and 
its cutting tace ^ inch below the borlzontal center line. The lint 
step win be to determine approximately the respective diameters ot 
the forming toot and then to correct them br the use of the tables. 

The diameters ot the piece are 1.T50, 0.750 and 1.250 respectlvslr. 

Bunt up or SMiUona 

and to produce these with a 3-iDch cutter the dlametera ot the toot 
would be approximately 2.O00, 3.000, and 2.500 inches respectlTslr, 
The first dimension, 2.000, Is 1.000 inch In diameter less than that 
ot the tool, and for the correction we would look in the column of 
dilTerences tor lucbee. but as the tables are only extended to hsU 
inches we will be obliged to obtain our correction in two steps. On 
the line tor U-lnch diameter, and under corrections for ^ Inch, we 
find 0.00854; and then on line ot 2^ and under the same heading, 
we find 0.01296, consequently our total correction would be 0.00SG4 + 
0.0129 S = 0. 02 150. This correction is added to the approximate diame- 
ter, making the exact diameter ot our first step 2.000 + 0.03160 = 
2.021G0 Inches. Our next step would be computed in the same way by 
noting on the 3-lnch line the correction tor >4 Inch and adding it to 
the approximated diameter ot our second step, giving ns an oxact 
diameter of 2.500 + 0.00854 = 2.60854. Thus our tool, to produce the 



piece shown in the example, would have three steps of 3.000, 2.0216, 
end 2.5085 inches, respectively, if it is to have its cutting face % inch 
below center. All diameters are computed in this way, from the largest 
or fixed diameter of the tool. 

In conclusion, attention should be called to the formed tool, illus- 
trated in Fig. 61, which is made in sections so that all diameters, sides, 
and angles can be easily ground after the tool is hardened. This 




Vlg. ea. Fonnlnff Tool and E&d View of Work 

design is of especial value when such tools are made from high-speed 
steel, as the finished surfaces are likely to be roughened by the high 
heat that is necessary for hardening. 

Formulas for Circular Forming Tools* 

The formulas required for circular forming tools may, perhaps, be 
expressed somewhat simpler than has been previously done in this 
chapter. Assume in Fig. 62, for instance, that the distance A in the 
piece to be formed equals the distance a on the forming tool, but as 

Fig. 68. Floca to bo Fonned 

this latter distance is measured in a plane a certain distance h below 
the horizontal plane tllrough the center of the forming tool, it is evi- 
dent that the differences of diameter in the tool and the piece to be 
formed are not the same. A general formula may, however, be de- 
duced by use of elementary geometry by means of which the various 
diameters of the forming tool may be determined if the largest (or 
smallest) diameter of the tool, the amount that the cutting edge is 
below the center, and, of course, the diameters of the piece to be 
formed, are known. 
If J2 = ]argest radios of the tool, 

a=dUforenco in radii of steps in the work, and 

* ICACBiNEar^ Jsnnary, 1908. 


If Om ■mailer radius r la given and tbe larger radlna A aontht, tto 
formnla takes tlia form: 

-» = v/ (v' r» - 6* + o )' + 6» 

Suppcwe, for an example, that a tool la to be made to form the piece 

In Fig;. 63. Assume that tbe largest diameter of the tool la to t>e S 

rtg. 04, DtacTHS Ibr Olroalai' rormtng Tsola 

Inches, and that tbe cutting edge is to be >il Inch below the center of 
the tool. Then the diameter next smaller to 3 inches Is found from 
the formulas giTen by Inserttng the glTen ralues: R=:l\i litch, 
b=:% Inch, and as^ inch (half the dUtereoce between 4 and SH 
inches; see Pig. 63). 


tratlon of their use will offer the best way of explaining them. Reisi^ 
ring to Chart Fig. 64, the distance A (see cut) thereon Is calcolmted 
from whatever the piece is we have to make. Under the word 'XHviaD,'' 
at the top and bottom of the chart, locate A, and follow down (or np) 
the vertical line until it intersects the proper curve. This point, car- 
ried to the right by the horizontal line, will indicate the corroetloii to 
be added to the diameter, after subtracting 2A, of course. The hori- 
zontal divisions for the verticals vary by 0.016 inch and the come- 
tions read to 0.001 inch which for practical use is as near as reqalred. 
The same illustration will answer for Chart Fig. 65; in this the cor- 
rection is carried around to the right of chart for larger values. 

The Chart Fig. 64 shows only five curves, and there is no quesUifti 
but what there are many other standards so it is quite Impossible to. 
make a complete chart or table. Unless we know all standards, how- 
rver, it is best to avoid useless calculations. 








Third Edition— Revised anC Enlarged 


Working Drawings, by Lester G. French - - 3 

Sizes of Working Drawings, by William L. Breath 20 

Draftsmen's Tools 23 

Drafting-Room Kinks 37 

Oopyrisbt* 1911, The Induatrial Press. Publishers of Machinery. 
49-66 Lafayette Street, New York City 


camera in this position and photograph the box. The result will be a 
view, Fig. 1, where not only the front edge of the box appears, but the 
Interior sides and bottom as well, indicated by the lines ABCD. The 
reason for this is that the lines of sight diverging from the eye of the 
observer reach both the front edge of the box, as indicated at A and B 
in Fig. 2, and the bottom, indicated at C and D, This is a view in 
perspective and from it one gets a partial idea, at least, of the shape 
and depth of the box, besides the shape of the front edge. 

In Fig. 3 is the same view of the box, but shown in projection. Here 
there is nothing to indicate what the depth of the box Is. The view 
gives a conception of the shape of the front, but* to form an Idea of its 
depth there must be another view taken at right angles to the front 

In Fig. 4 is shown how this view in projection may be supposed 



Fiff3 1 to 4. Views in Perspective and In OrthoRrjHKJ? ^'^J**^®** 

to be produced. The box is placed on the table, iimS^ front of it, 
and parallel with it, a piece of glass. Let a person stdS?f^ ^^*^ ^^ 
eye will come directly in line with one corner X of the ?!?• *® ^ ^^® 
illustration, and make a dot on the surface of the glass. Ty^^^^^ ^^ 
point 1, where the line of vision passes through the glass tcmj^*® ^®^" 
ner. Now let him move until his eye comes exactly in front^Pf PO^*^* 
r, and mark point 2 on the glass, and so on, all the way^^^"^*' 
Then, by connecting points 1, 2, 3 and 4 he will have a covrect^^^^^ 
sentation in projection of one edge of the front of the box. ^ 

The lesson taught by this is that a projection drawing giv?* ^® 
idea of distance to or from the observer in a single view, but f^P*^ 
sents, simply the distance in any direction in a plane surface i^® ^ 


tbe outside edges In Fig. 6. The views are bo arraoged In Fig. 6 thai 
if the top view be placed directly on top of the block aod then the 
sheet of paper be folded over on the line x y, ths front view will oeme 
directly in front of the block; and then If the sheet be again folded 
or bent back along a 6. tbe left-hand end view will come In front of 
the left end of tbe block; tLnd Ctnall;, It It be folded back along c d, 
the right-hand end view will come in front of tbe right-hand end of 
the block. If the block were inclosed In a box having transparent 
Bides and tbe outlines of the block were traced on each of the sides aa 
they appeared to an observer looking through the successive sides ot 
the box, and flnally the sides were unfolded so as to lie fiat in one 
plane, tbe views would appear as In Fig. E. 

To produce the arrangement shown in Fig. 6 we may assume the 
block to rest on the paper with Us top side uppermost. If we then 

Fig. a 

. Angle Pr«jM 

mark around the block with a pencil we will get the top view shown. 
If the block then be tipped over with Its front side uppermost and 
we mark around it, the front view will be obtained. Again, If it be 
tipped first on one end and then on tlie other tbe two end views will 
be obtained. 

A close study of Figs. 5 and 6 will show how necessary It Is to 
adopt some one .''ystem and to adhere to It, as otherwise there will 
very likely be much confusion in tbe shop, and perhaps mistakes made 
by the patternmaker. 

Conventional Lines 

The various styles of lines used In working drawings are shown In 
Fig. 7. Tbe ordinary line (1) Is for outlining objects, for section 
lining, and tor all ordinary purposes. The shade line (3) is used to 
represent the edges supposed to separate the light from the dark 
surfaces ot an object^lhat is, the surfaces on which the light strikes 
from those In shadow, as shortly to be explained. The dotted line (3) 
Is chiefly for representing the details ot an object when the? are so 
covered as to be obscured from view. Many details can be represented 


ance of the drawing, and they also indicate which are the raised and 
which the depressed surfaces. This will he clear from Fig. 8, in which 
several examples of shading are shown. At A is a square block, hol- 
low in the center. The outer shade lines show that the block is raised 
above the surface of the paper, and the location of the inner lines 
shows that the center of the block is depressed below the outer surfftoe 
of the latter. At B is shown how the block would be shaded if at an 
angle of 45 degrees. Since the projection of a ray of light is supposed 
to be at 45 degrees there is no logical reason why the lines c c should 

a b 

G <» 

PiO'.'STrutL pnfSNv 

Figr- 8. Shade Lines 

not be shaded instead of those shown; but the figure looks well as 
drawn. At C is the shading for a hexagonal prism, and at D for a 
hollow cylinder. The shading on the top view of D starts at the 
45-degree line a h, gradually increases, and then diminishes to nothing 
when it again reaches the line. The right-hand element of the cylin- 
der in the lower view of D should not rightly be shaded, because it 
really separates two dark surfaces, the shadow actually starting on the 
element c d. In practice, however, the right-hand element is the one 
shaded. At E are two blocks a and h of the same size. No shade 
would be used to separate them; but at F. where blocks at a and b are 
of different thicknesses, the shade line would be necessary. At 


the block h is recessed for the cylinder a. It may be shaded as shown, 
although some draftsmen might prefer to leave oft the shade line cd 
in the lower view. 

Screw Threads 

Conventional methods of representing screw threads are shown in 
Fig. 9. These are the most common methods, although there are some 
others less frequently met with. Methods A and B are generally 
employed, and of the two that of B is to be preferred, as it is more 
easily done. Some draftsmen place the heavy lines shown at B. repre- 

y H 




Fig. 9. Conventional Indications of Screw Threads 

senting the bottoms of the threads, on the right-hand side instead of 
on the left-hand side, as it then gives the effect of shading. At E is 
a conventional square thread. If any long piece is to be threaded the 
entire length, the threading can be indicated as at F, which saves 
drawing the complete thread. The difference between the representa- 
tion of a single and a double thread is indicated at G and U. The 
single thread is at G. and the inclination of the lines is such that the 
line ty^ at right angles to the axis of the piece, passes through the 
top of the thread at one side and the bottom of the thread on the other 
side of the bolt. At H the inclination is such that the line j: y passes 
through the tops of the threads on both sides of the bolt. At K is 
shown a right-hand rhread, and at L a left-hand thread. 


Tapped Holes 

At A Z? C D, Fig. 10, are methods of representing tapped holes where 
they are obscured from view and must be shown by dotted lines. 
Those at A and B are much used, but where the drawing is crowded, 
those at C and D are to be preferred, and in any case they make a 
neater appearance. Top views of surfaces having tapped holes may be 
indicated either as at £7 or F. If as at E, a circle should be drawn of 
a diameter equal to the outside diameter of the bolt, and the hole 
marked as indicated, which shows that the hole is to be tapped and 
also indicates the size of the bolt to be used. If the method at F is 
employed, the inner circle should be approximately equal in diameter 
to the diameter of the bolt at the base of the threads, and the outer 
dotted circle should be equal in diameter to the outside diameter of the 
bolt. At G is the top view of a tapped hole as it appears in a sec- 
tional view. At // is a representation of a threaded piece which ex- 
tends through a block threaded to receive it, as shown. At K Is a 

■rTap \ 


' - - ...... ^ y^ y^ . 


Fljf 10. Representation of Tapped HoleH 

vertical section through a tapped hole. This is for a right-hand thread, 
although the lines incline as though it were a left-hand thread. This 
is simply because only that part of the thread is visible which is at 
the farthest side of the hole where the threads must, of course, in- 
cline in a direction opposite to the direction they take at the front 
side of the hole. This can be clearly seen by examining a bolt or nut 
At L is shown a section through a tapped hole into which a bolt has 
been screwed. 

Broken Sections 

In Fig. 11 are shown methods of representing bars and rods, shaft- 
ing, structural beams, etc., when it is not convenient to show their 
whole length on the drawing. In such cases these pieces would be 



or on another part of the same sheet, the details could be drown sepa- 
rately and properly dimensioned. That would be one way to make 
the drawings. Another way would be to make a general view of the 
rod as before, but to show the end as though it had been cut or sliced 
in a 'Plane parallel with the paper, and the upper parts removed, 
exposing the details. The parts cut through would be ""cross-seo- 
tioned," bringing them into bold contrast, and the dimensions could 
all be placed on this one drawing. Such a method is possible with a 
simple construction, having but few parts, and is often adopted to 

Sectional views may also be used for much simpler purposes than 
above outlined. They may be used to show the shape of the arm of a 

Sec+ion on c-d 



FiflT- 12. 

Section on o-b 

Tig. 13. 

Methods of Showing^ Sections 

pulley or of any other part of any casting that can be conveniently 
represented in this way. The cutting plane may be assumed to lie at 
any angle necessary to bring out the details most clearly; or, if de- 
sired, a sectional view may represent a casting as though it were 
cut through a part of the distance on one plane, and the rest of the 
way on another plane, either higher or lower, as convenient. All that 
is necessary to have the view clearly understood is to draw a line 
through one of the views of the piece, indicating just where the sec- 
tional view is supposed to be taken, and then to make a note on the 
drawing to that effect. 

In Fig. 12, at A. is a plan view of a hand-wheel. As the wheel is 
symmetrical, it is quite unnecessary to draw more than half the wheel, 
although the whole wheel may be drawn if desired. It is here repre- 
sented as though cut in two along its diameter on the line a h. This 
line should be a dash-and-dot line, as shown, and not a solid one. It 
has been pointed out on page 7 that one of the uses of a dash-and- 



dot line is as a center line where a piece is symmetrical, and its use 
here would indicate that the half of the wheel not drawn was like 
the part that was drawn, even if it were not otherwise apparent; for 
under no other condition would the figure be symmetrical. 

At B and C in Fig. 12 are shown sectional and edge views of the 
hand-wheel and the different ways in which they may be represented, 
according to the fancy of the draftsman. In B, to the right of the 
center line cd, is an edge view of the wheel in which the shapes of 
the rim and hub are shown by dotted lines, since they would not be 

iNDvsTihAL pecs$ M y. 

Section at A- B 

Plff. 14. Conventional Sectioninflr ot Qear AVheels 

visible to an observer who held the wheel so that he looked directly 
at the edge or rim. To the left of c (i is a sectional view taken along 
the line at in A. 

In the view below this, at C, are shown two methods of drawing what 
are termed "dotted sections." The sections are supposed to be taken 
on the line a & as before, but cross-sectioning is done ])y dotted lines, 
indicating that the shape of the section would ho as shown, but that 
the parts in front of it have not actually bo^-n cut away. This is a 
very convenient convention to adopt at times. For example, in show- 
ing a milling machine knee and saddle it would enable one to repre- 
sent the knee and saddle as they actually appeared, and also to show 
a aectional view of the mechanism \inder the saddle and inside the 
knee. If, on the other hand, the view were drawn as though the knee 
were actually cut through, one would not form an idea of its exterior 
appearance unless another view were drawn. It will he noted in the 
figure that the dotted lines extend clear across the section, as drawn 
at the left of e/. and only along the edge of the section at the right 
of c/. 

In Pig. 13 is a pump valve-seat having four webs connecting the 
outer rim with the hub. There are two ways of showing a sectional 



view of a piece in which webs occur. If the view were taken along 
the center line ah and sectioned, as usual, nothing would be gained, 
since it would give no idea of the shape of the webs. Some, therefore, 
prefer to take the section to one side of the web, as on the line cd^ 
and as shown in the upper sectional view. This indicates clearly 
what the shape of the web is. Others, however, prefer to adopt the 
expedient illustrated in the lower sectional view. Here the section 
is supposed to be taken along the line a 5, but where the plane cuts 
through the webs, the sectioning or hatching is done with the lines 
further apart than in the balance of the section, thus making enough 
distinction to show what part of the plane passes through the ^'ebs 
and what part doos not. Both methods have their uses under suitable 

In Fig. 14 are two views of a gear wheel. The one at the left side is 
a side viow. and as all the teeth are, of course, alike, it is unnecessary 

l'>OCSTf^L fVtSS M Y 

FIk- 1&- R«»preaontation of Bolt« in Sections 

to draw more than a few of them. The pitch line of the teeth is repre- 
sented by a dash-and-dot line, this convention always being followed. 
In the part of the rim where the teeth are not drawn, the face of the 
gear is Indicated by a solid line, and the position of the roots of the 
teeth by a dotted line. Some, however, prefer slightly different con- 
ventions. To show the shai)e to which the arms are to be formed, a 
sectional view of one of th«' arms is drawn in this view. The end of 
the shaft is sui)i)used to be broken off and is sectioned. 

The right-hand view, in Fig. 14, is a sectional view taken along the 
line A 2?. It will be noted that the shaft and key are not sectioned. 
The method followed in such cases is usually to section the castings 
or inclosing parts, such, for example, as the hubs, rims, etc.. o.f a 
wheel, but not inclosed partb like shafts, rods, bolts, keys etc. k 
bushing being both an inclosed and inclosing part might or miguV 
not be sectioned, individual judgment dictating the method here as 



elsewhere. This gear has five arms, and the line A B cuts through one 
of them only. They are not sectioned in the right-hand view, and two- 
opposite arms are drawn as though hoth of them lay in the plane of 
the paper. While this is not correct, it is the method usually followed. 
The method of representing the gear teeth in sectional views is gen- 
erally as shown in this cut. 

In Fig. 15 are sectional and top views of a cylinder or pipe on which 
a blank flange is bolted. There are five bolts, and the plane in which 
the sections are taken would cut through only one of them. Most 
draftsmen, however, would draw the sectional view as indicated at 
the left. The bolts are shown as though both were in the plane of 



WfySTTPJ"!. ^^^ I* ^■ 

Flif. 16. Section of I'naymmetiical 

F^jf. 17. DiraenslonH of Holes in 
a Circle" 

the section, and these bolts are not stMtioiuHl, but arc drawn in full, 
as explained above. It is not necessary, moreover, to sliow more than 
two of the bolts, since it would detract from the clearness, and the top 
view shows plainly how many bolts there are. Some draftsmen think 
bolts drawn in this way are too prominent, and prefer to represent 
them in sectional views as shown at the right in Fig. 15. This method 
also has the sanction of fairly common u.sage. 

Fig. 16 is another example of a figure that is not symmetrical In 
all respects. It shows two views of a step bearing having three ears 
or lugs for bolting it to its base plate. In making a sectional view 
of such a piece should the cutting plane be supposed to pass through 
the lugs? In most cases, yes, and according to common practice the 



sectional view would be made symmetrical, and the distance A in the 
lower view, from the center of the piece to the outer end of each lug, 
would be made equal to the distance A in the upper view. 

In any machine various kinds of metal and other material are used, 
and when sectional views are made it is convenient to have some stand- 
ard method of cross-sectioning the different parts to indicate what 
the metal or material is. Conventional sectionings adopted for this 
purpose are given in Pig. 18, the system here represented following 
very closely that used by the U. S. Navy Department. It should be 
said, however, that draftsmen are coming more and more to section 
all parts alike, adopting the style used for cast iron for all kinds of 
material, and then printing on the pieces themselves what the material 
is of which they are composed. This avoids the possibility of mistake 

y///////<- /A'/ 

Cast Iron. 

BrQ9S or Composition . 

Rubber or Vulcanite. 

Wrought Iron. 



steel. Lead or Babbitt. 

Flgr. 18. System of Indicatlntf Different Materials by CroBS-aectloninfir 



through failure to understand what the conventional methods of sec- 
tioning are supposed to represent. 


The most important part of a drawing is the dimensions. They 
should be given so fully and completely that a workman will never 
have occasion to measure a drawing. The dimensions should include 
an "over-all" measurement and the different measurements that make 
up the "over-all" size. Dimension lines, and the exteiwi t e n lines which 
the arrow heads of the dimension lines touch, are usually fine black 
lines made up of long dashes. They should be so drawn as to appear 
secondary in importance to the drawing itself. Some draftsmen draw 
all these lines in red ink and use a solid instead of a broken line. In 
a blue-print the red lines will appear lighter than the black ones, 
making a good distinction. 

In Fig. 19 is a sketch of a bushing. The diameter of the bore is 
given at U by a dimension passing through the center of the circle. 



It is somewhat confusing, however, to have more than one dimension 
line passing through a center and therefore it is better to give the other 
diameters elsewhere, if possible, as at E, F, and G. The length of the 
various steps of the bushing are given at A, B, and C7, and it will be 
noticed that they are slightly offset — that is, the dimension lines 
do not extend in one straight line. This makes a very clear arrange- 
ment. The over-all dimension is at D. Methods of placing dimeu- 







•• — A 


n — - 


INSJiTftiAL PnSSh i 

<■ c 

Plar- 10. Sample Drawing, Showlngr Location of Dimension Lines 

sions on holes that are drilled in a circle or a row are shown In Figs. 
17 and 20. That in Fig. 17 requires no explanation. In Fig. 20 cen- 
ter lines are drawn in each direction through the centers of the holes 
and the dimensions are given from center to center each way, and 
also from the edges by which the holes are to be located. 

Fig. 21 refers mainly to the dimensions of the bolts. At A is a 

Fl|r. 20. Dimensions of Holes Located in Straight IJnos 

hexagon head bolt, so drawn that three sides of the head are visible. 
Bolts are usually drawn in this way because they look well, and as 
most bolts used in machinery are standard and taken from stock, no 
dimensions are necessary other than to specify the diameters and 
lengths. These may be printed on the drawing, or better yet on a 
list of bolts and other small parts, sometimes called an order list, 
which should accompany the drawings. Every bolt and machine scmw 



should be specified in some such way. At B is a hexagon head bolt, so 
drawn that only two sides are visible. If it is a special bolt it should 
be represented like this so that the dimension across flats can be given, 
to which the head is to be milled. At C and D are two ways of draw- 
ing a square head bolt, according to whether the dimensions across 
flats arc necessary or not. In cases like B and D the abbreviations Hex. 
and Sq. should be used as shown, so that there will be no mistake 
about the style of head desired. 

The length of a bolt should be given from under the head, as at £7 
in Fig. 21. The total length should be given and also the length from 
the head to the beginning of the thread, showing how high up the 
thread is to be cut. At F in Fig. 21 is shown how to give a dimension 
when the space is narrow, and at O and H how radii may be denoted. 

k- /'Hex- 






Vlg 21. Dimensions of Minor Details 

There are various, rules about the dimension figures themselves, to 
which allusion should be made. First of all, the figures should be 
plain, so that no mistake can be made in regard to feet and inches. 
The usual practice is to represent feet by the prime mark (') and 
inches by the double prime mark ("). Some hold that this is not dis- 
tinction enough and insist on the u>ie of "It." for feet while retaining the 
inch mark. Some also object to the slanting line between the numera- 
tor and denominator of fractions, holding that the line might be mis- 
taken for the figure one, if carelessly made. Some prefer the horizon- 
tal line, and others write the numerator over the denominator and 
omit the separating line entirely. It is customary to arrange all the 
dimensions to read either from the bottom or the right-hand side of 
the drawing, though it is possible to have everything read from the 
bottom by making the figures upright, or up and down on the sheet, 
regardless of the direction of the dimension lines. In the shop, inches 
are used more than feet in measuring, and dimensions are usually in 
inches, except for large work. In some shops they are given in inches 
even up to 10 feet. 



IndicatinfiT Finished Surfaces 

A drawing is or should be so marked as to tell the workman what 
surfaces are to be finished and what kind of finish is desired. This is 
often done by writing a character, resembling the letter /, across the 
line representing the edge of the surface to be finished, as in Fig. 22. 
Another way is to write the words "polish," "finish," "ream," etc., near 
the edges of the surfaces to receive the treatment indicated. Still an- 
other method that is much in use is to draw a red line near the edge 
of each surface to be finished. When a blue-print is taken from such 
a tracing, the red lines will print fainter than the black lines, and 
a draftsman can easily trace over them on the blue-prints with red ink. 
Still another method that can be used to advantage in a manufactur- 



Polish. INDUS TRIAL Plf£5S N. Y. 

Piff. 22. Methods of Indlcatlngr Finished Surftices 

ing plant is to put only the dimensions of finished surfaces on the 
drawing, leaving off entirely all dimensions of rough surfaces that are 
of service to the patternmaker, but to no one else. The workman in 
the shop then knows that wherever he sees a dimension the surfaces 
are to be machined. One feature that should be looked after more 
carefully than is usually done is to indicate how closely the various 
parts must be finished to size. If a piece must be made within a half- 
thousandth of an inch the workman ought lo know it, and If a thirty- 
second of an inch is near enough he surely ought to know it. The 
practice of giving dimensions in thousandths of an inch where needed 
and of using plus and minus limits where sizes are to be kept within 
limits, putting the limits on the drawing, is a good one to follow. 



Manufacturers do not have any universal standard of sizes for work- 
ing drawings. From time to time there have been recommendations 
made by various societies regarding standard sizes, but these recom- 
mendations have had little effect in bringing about any generally 
accepted standard in drafting-room practice. Many firms use large 
and unwieldy drawings, which are as difficult for the draftsmen to 
work on as they are cumbersome to handle by those who are to use 
them. Of course, most drafting-rooms have their own standard sizes 
for the sheets. There is usually a small sheet for sketches and details 
and then larger sizes which are multiples of the detail size. These 
larger sizes are used for the assembly drawings and for detailing large 







PATT. 1 6-43. 

JAN. 1909 


Figr. 23. Master Drawing of Simple Machine Bed 

pieces. It is, however, difficult to take care of all these various sizes 
of drawings, a difficulty which can be avoided by having only one size 
sheet, of a convenient size for both the draftsmen and the shop. 

The size of the sheet to be adopted should be chosen first of all with 
regard to economy in cutting the sheets from commercial sizes of 
paper and tracing cloth. Tracing cloth comes in rolls 30, 36, 42, or 48 
inches wide, and there is thus a wide range to choose from. The 
standard sheet used by the U. S. Navy department, and, the writer 
believes, also by other departments of the government, is 21 by 27 

All manufacturers working on orders for the Navy must send trac- 
ings of their work on this size sheet, and some manufacturers, there- 
fore, have adopted this size as their own standard. It can be cut with- 

• Machinery, March, 1909. 



number 27-35, and having as many supplementary sheets. A, B and C, 
as necessary. 

In case there is room on one sheet for more than one detailed 
section, these sections will be noted on the master drawing by the 
letters A-A, A-By A-C, etc., the letter A being used for each section on 
sheet A, If the piece to be detailed is too large or complicated to 
have the three views clearly outlined on the master sheet, then each 
view will be made on a separate sheet, and the plan view will be con* 
sidered the master drawing; the other master drawings have the same 
serial number, with a number added, as for instance, 27-34-1, and 27- 
34-2. In this way every part of the machine will be fully shown, as 
well in its relation to the other parts as in detail. In fact, the main 
purpose of the master drawing is to show the relation of the different 
parts of the machine to each other. When the master and detail 



26 X 20 





Flff. 26. Convenient Arransrement of Draftinsr-room 

drawings of a machine are fully completed, they can be bound together 
by any suitable loose-leaf method, and if desired for reference, an in- 
dex of the pieces can be made on a standard sheet. 

Fig. 25 shows a convenient arrangement of a part of a drafting- 
room, where the small sheet system has been adopted. The design- 
ing draftsman's board is not shown. He, of course, must have a board 
as large as is convenient for the actual designing work. Running 
around the room, and under the window sills, is a shelf 16 inches wide, 
with drawers under, large enough for the standard size drawing. The 
draftsman's tools and books can also be kept in drawers under the 
shelves. Being at the left hand of the draftsman, the shelf is a con- 
venient place for reference drawings, books, etc. 

The system outlined has been objected to on the ground that it is 
not advisable to have the various views on separate sheets; much 
time is lost finding the sheets required to show the detail complete; 
the draftsman's time is unnecessarily wasted, etc. This criticism is 
partly justified, and it would be impossible to recommend th^ system 
for all classes of work and all conditions. Each individual drafting- 
room must decide for itself whether the work peculiar to it could be 
advantageously handled in the manner described. 



cut. These scales are of the reverse bevel tsrpe, and both sides of 
each scale are graduated the same, but read from opposite ends. With 
this arrangement it is never necessary to more than turn the scale 
over to have it reading in the desired direction. The divided foot on 
the 1%- and 3-inch scales is marked 2-4-6, etc., instead of the usual 
3-6-9, which makes it easier to find the desired point. The 6-inch scale 
is fully divided into IGths and the 12-inch into 32ds. Scales of this kind. 

yL«,'PR'i'i'i'i"T''i — I — : 

■^ — n — r 





T — r 


— I — I — ^ 




j> n 




•I'l'i'p'i'iYii'i'ii'iv'i I'li'.'i 

JO.. »_.'■-_! i? 

V^ P' 'P ' P T' T ' T ' T ' T ' T ' 'nTiT ' '|' ''l ' '' r ' ''*'l ' ''' '''l • '^ ' ' ' ''I ' ' l 7 J 

-4 n' 

V I 

I'l'i'in" ; ' 1 

i''T"'';'i'"'"'i" ') ^ [HI 



\ 4.' 4-i .t: 



Fisr. 2n. Set of Dral tsninn'a Scales 

however, art." made only to order by the firms manufacturing drafts- 
man's scales. 

A slide rule, a protractor, and a couph^ of curves complete the set 
of tools. 

Special Draftsmen's Tools 

While the set of tools described above is an excellent collection for 
general requirements, many draftsmen need special tools for special 
purposes. In the remaining portion of this chapter, a number of 
diflfereut tools and also a number of general drafting-room conveni- 
ences and devices are described, \vhich will be found useful for the 
purposes for which they are intended. The descriptions of these tools 
have been contributed from time to time to the columns of Machinery. 
and the names of the contributors, together with the month and year 



der around Fig. 27 was made by a border line pen of the description 
shown in the same figure.* 

Attachment for Draftsman's Scale 
Fig. 29 shows a very simple means of converting the ordinary drafts- 
man's scale, graduated to 1/16 and 1/32 inch, as manufactured by the 
Brown A Sharpe Mfg. Co., into a scale that can be used for scaling 
or making drawings half size. The attachment consists of a narrow 
brass or steel strip with four or more pins inserted and riveted to it 


j'l'i':'j'|i|'i'j'|'|M'[':' r i' [ ' i '['i M 'i' j 'l' |' i'|' i' |'i ' [ 'iM i:i;i r :' 
/r=>^ 1 2 a 4 

.. -. — - _ 






« 1 

! M ! 1 1 : 

1 li 1 1.1 I 

1 1 ' 1 i 1 1 

Il 1 ! 1 1 1 

1 lilil 

Plsr. 20. Improvised Half-size Scale 

These pins fit into holes which are drilled in the scale. A still better 
construction could be obtained by forming heads on the rivets, and 
having buttonhole slots in the scale. If it is desired to adapt the 
scale for half-size work, number each ^2 inch consecutively as full 
inches. For quarter size, each % inch should be consecutively num- 
bered with whole numbers. Applied, as shown, on the 1/32-inch side, 
each graduation reads as 1/16 inch. 

Scale for Beam Compass Bar 
Beam compasses can be improved by placing a scale on the beam 
as shown in Fig. 30. A linen tape measure will answer the purpose. 


Machintrff. Jf Tm 

Flfif. 30. Scale for Beam Compass Bar 

A coat of shellac keeps it clean and the divisions distinct. The object 
of the graduations is simply to get the pencil point approximately set, 
the finer adjustment then being made. 

Weighted T-square Head 

The cut. Fig. 31, shows a T-square having a IMj-inch hole drilled in 

^♦he upper part of the head, and a piece of steel inserted. The upper 

• Albert C. Sharp July, 1906. 



part of the bead being the heaviest, it always tends to keep the upper 
edge of the blade down close to the board.* 

Guide Strip for Drawing Board 
A great many draftsmen are quite frequently troubled iSy lines 
drawn with a T-square not being parallel with each other at different 
points of the drawing board. This is invariably due to the fact that 


Lt-aO ot Ste«l 


e o 


.VacAin»ry .N V 

Piff. 31. T-square Head Weighted to Hold Down Upper Edge 

the edge of the drawing board is seldom true. This trouble may be 
easily overcome by the application of the T-square guide shown in 
Fig. 32. The left-hand side of the drawing board is cut out 5/16 inch 
deep by 1% inch wide, the full width of the board, and a bar of steel 
% inch by 1% inch, length to suit, is inserted; the latter is secured 





Drawiiii; l3<Mird 

M-fhtrntr;,, .\. i". 

Flff. 82. Oulde Strip for Drawing Board 

by four screws, the holes for the screws being oblong to allow for any 
ezpassion or contraction of the drawing board. This guide, projecting 
^ inch from the edge of the board, gives a smooth surface for the. 
T-square head, and projecting 1/16 inch above the board, as shown. 
* Gofdon F. Monalun. Augast, 1906. 


tends to keep tbe T'Square blade Just enough above the paper to keap 
the drawing paper, which Is very olten soiled by the shifting of Um 
T-square, reasonably clean. Parallel lines at all points on the board 
are Insured by the application of this guide.* 

Arrangement for Holding T-aquM-e in Place 

Fig. 33 b1)o»s a very siiiii)le, cheap and effective arrangement tor 

holding tbe T-square against the edge of the drawing board. Tbe nutr 

terlala needed are a small wooden grooved wheel, a sufficient length 

■■f heavy cord about 3/32 Inch in diameter, a colled spring to give suffl- 

dent tenslou to the cord, and a few screws, nil arranged as shown 
in the cut. A strong rubber band can bp used in place of the spring, 
but, of course, is short-lived. The whwl Is fastened in the center of 
the under side of the T-square head. On small boards it may be 
advisable to fasten a small triangular block at the lower left-hand 
corner of the board so as to allow the T-square to be used when tbe 
drawing is near the edge of tlic board. 

To one accustomed to the old method of moving the T-square by 
grasping the head and continually lining it up, the advantage of thia 
simple device will be a surprise, as the T-square can be moved easily 
by applying the hand at A. about eight inches from the head, and 
when moved out of line it automatically returns to Its proper place. 

' '. C. Hassplt. Sloy, 11)07. 



An important advantage is, that in keeping the head snug against 
the edge of the board, the wear on the ends of the head where it 
slides on the board is avoided. This wear is caused on the ordinary 
T-square by the uneven pressure when sliding it up and down. The 
edge gradually becomes slightly curved, resulting in non-parallel lines 
on the drawing. Most draftsmen are not aware of this defect. The 
T-square is quickly detached by simply lifting it oft the board, the 
cord slipping easily from the wheel. To find the proper tension for 
the cord, the T-square should be put in the center of the board, the 
cord fastened to the lower edge of board and brought around the wheel 
to a loop in the end of the spring which is fastened at the upper edge 

• t/' ttuAcT t 3'fULLEYS. grooved for '"^' 

» ^K. .:^ -: ^ 

- X 


Y - t . 1 

- ■ - i'ry." * 

Fiff. 34. Elevations of the Drawingr Board Frame or Easel 

of the board. Now swing the T-square around so that it lies at an 
angle of about 30 degrees to the center, keeping one end of the head 
against the edge and near the center of the board. Increase the ten- 
sion on the cord until it is sufficient to cause the blade to swing quickly 
into place. In other words, it should be so tensioned that no matter in 
what position the T-square is left, it will immediately return to its 
proper position. This scheme can be applied to any common T-square 
up to 42 inches long, and, in fact, even to longer T-squares, provided a 
tension spring of proper dimensions is selected. Of course, it is pref- 
erable to use as light a T-square as possible. Note that the cord is 
not wound around the wheel, but simply bears on it exactly as trolley 
wire on a trolley wheel. 

Large Compact Drawing Board 
To meet the conditions requiring large capacity and minimum floor 
space, tlie board shown in Figs. 34 to 36 was built. The frame, 6r 



easel, as acUsts would term it, is shown in Fig. 34. Only general 
dimensions are given, for such details as placing screws and making 
joints can be decided by the workman. The shaft, pulleys, and bear- 
ings, shown at the top, carry the counterweights needed to balance 
the drawing board. Fig. 35 shows the general dimensions of the board 
and straight-edge. The board is built of %-inch stock in the usual 
manner, with a brace at each end and one in the middle. The end 
braces also act as guides, their centers coming in line with the cen- 
ter line of the pulleys on the shaft shown in Fig. 34. A 25-pound 
window-weight at each end serves as a counterbalance for the board 
which is thus easily raised or lowered. 

The slraight-edge requires care in making, as both the upper and 

-. , -1 0--- 




I I 





^ LINE 18 




Maekknerff, A.Y. 

Fig. 35. Detail of the Drawintf Board and Straight-edge 

lower edges should be parallel. The projecting shelf is intended pri- 
marily as a brace, but it is also very handy for holding tools. By 
means of the line and small pulleys, shown in Figs. 35 and 36, the 
straight-edge is moved and kept in a parallel position at every point, 
the line being clamped at each end of the straight-edge by a brass 
screw and nut. The straight-edge is counterbalanced by a weight of 
cold-rolled steel hung from a cord attached just above the brass clamp- 
ing nut. 

The material used was as follows: 25 feet of pine, 15 feet of white 
wood. 2 pounds of brass used in the small pulleys and bearings, 53 
pounds of cast iron in the drawing board counterweights and large 
pulleys. 4 pounds of cold-rolled steel 1 inch in diameter for the straight- 
edge counterweights, 7 pounds of cold-rolled steel % inch in diameter 
for the shaft at the top of the frame, 25 feet of window cord, 35 feet 
of best quality fish line, and 3 dozen wood screws. 





so as to impair the accuracy of the angles. The dotted lines in the 
view to the right show how the celluloid will shrink. After the cellu- 
loid has finally set, very little care is required to keep the angles 

Muchtirr^, A. F. 

Figr. 37. Draftsman's Triangle 

It is not necessary to tell a draftsman how to true up the outside 
edges. To true up the slot angles, the first thing to do Is to draw a 
base line with the T-square. From this line lay oCC carefully all the 
angles that are on the triangle. With a file work out the slot edges 



Fig. 38. A Handy Triangle 

7f.u«WHB/ /Vm#. .V. ]• 

of the triangle so that, when laid against the T-square, the edges will 
match the drawn lines perfectly. Any waviness or inaccuracy is 
clearly shown by this method. 
The knob should be riveted in, but do not hammer hard enough to 



buckle the celluloid. The hollow side of the celluloid should be down, 
as the triangle will then lay flat.* 

Fig. 38 shows another handy triangle of less elaborate design. It is 
a 30 by 60-degree triangle, having internal angles of the same degrees, 
but opposite to the external ones. With a triangle of this form hexa- 
gons, screw heads, the bottom of drilled holes, etc., can be easily and 
quickly drawn, as it is not necessary to reverse or turn over the tri- 

iVac/itMo-y. .V. r. 

FlfiT. 39. Triangle for I-beam Sections 

angle, but merely to slide it along. Every draftsman doing detail 
work will find this tool a valuable addition to his kit. 

Triangle for Drawing I-beam Sections 

Fig. 39 shows an alteration on an ordinary triangle which makes 
the drawing of the sections of I-beams and channels much easier than 
the usual way. The slant is that of the flanges of the standard rolled 
sections, i. e., 16 2/3 per cent or 2 inches per foot. This triangle is of 




_ T 


FiffS. 40 and 41. Ordinary Trlan^Iu. an<l Triangle for Drawing Thrt'Bds 

service to those. draftsmen who have some structural work to do, but 
not enough to warrant the purchase of a special trlanple.f 

Triangle for Drawing ThreadB 

Meet draftsmen have more or less trouble in drawing the common 
representation of small screw threads. The cuts, Figs. 41. 42. and 43 
show a simple device which makes this operation much easier, quicker, 
and not so tiresome. The threads also can be made more uniform. 

• W. L. Breath. November. 1007. 
t Rofper D*!. French, October. 1005. 

..JL rf -t . k 



Any draftsman can make this tool himself. Take an ordinary celluloid 
triangle, as shown in Fig. 40, a 45-degree triangle is preferable as the 
opening, ABC. in the center is larger, but a 60-degree triangle can be 
used. First drkw lines on the triangle as represented by the lines 
AB' and B' C in Fig. 41. These lines can be scribed on with any 




Fiffa. 42 and 43. Trlanfiflo In Tig. 41 used for Drawlnsf I^ft- and Rlffht-hand Threads 

sharp instrument, and should be at an angle of about 4 degrees with 
the horizontal. Now take a sharp knife and cut away the celluloid 
very carefully until having almost cut down to the lines. Then take 
a fine file and finish off to the lines, making the edges smooth and 
straight. Either horizontal or vertical threads may be drawn with- 

Maekimtrp S.F, 

V\K 44. Draftinff Tool for Ratchet Teeth 

out changing the position of the triangle, and right- or left-hand threads 
are drawn by simply turning it over.* 

Tool for Laying Out Ratchet Teeth, Tangents, etc. 

Fig. 44 shows a little instrument which is a great time-saver^ It is 
used in putting in both radial lines and tangents about a given center, 

♦J. W. Colr-mnn. AuRust, 1000. 



as in drawing the teeth of a ratchet wheel, etc. The slotted bar, B, 
has a pin, P, held in one end of it by the screw, 8; this pin is stuck 
into the paper at the given center. The triangle, T. is shifted length- 
wise on the bar and turned about the screw C until one of its sides 

J/rti Ai><ry, A. J . 

Fie- 45. Section Liner 

takes the direction of the radial or tangent which it is desired to repeat 
about the center. The triangle is then clamped firmly in position on 
the bar by means of the knurled nut, N, and then, by swinging the 
entire instrument about the fixed pin, the edge of the triangle Is 
brought to the successive positions at which it is desired to put in 

Fig. 40. Simple Section I.iner 

the required lines. The slotted bar. B, may be niado Ioii^^t than it is 
here shown, but, for nearly all ordinary drafting-rouin work, the length 
shown is sufficient.* 

Section Liners 

The device shown in Fig. 45 has given excellent results as a section 
liner. It is used on drawing paper entirely independent of a T-square. 
As seen from the cut, the device consists of a ratchet wheel A. a pawl 
spring B, two knurled rollers C, and the pen guide or ruler D. The 
teeth of the ratchet are milled as shown in the detailed view. The 

* Claude T. Johnson, July, 1006. 



ratchet and knurled rollers are fastened to the shaft E, and as the 
device is pulled hack across the drawing paper for each line drawn, 
the ratQhet pawl descends into each of the little grooves in the wheel, 
thus spacing the lines evenly. For different spacing, differently pitched 
ratchet wheels are used. By using thin rubber bands over the knurled 
rollers, the device will work well on tracing cloth.* 

A much simplor section liner consists of an old instrument screw 

MnetAfurf, N. T. 
FliT 47. A Simple but Efficient Section Lloer 

turned into a slightly smaller hole in a piece of wood a little thicker 
than the diameter of the screw-head, and of such size that the two 
can be used in the central hole in a triangle as shown in Fig. 46. The 
screw provides for a very fine adjustment of the spacing.f 

Fig. 47 shows the principle of a section liner which, although sim- 
ple, answers the purpose fully as well as some of the more complicated 
and expensive arrangements. It consists of a piece of brass, or any 
metal, 12 inches long, with threads cut on one side as shown, about 40 
threads to the inch, and a wooden triangle and a pin driven in as 
indicated and filed to fit the thread into which it is to engage.^ 

• Charlos A. Kolley. Xovnnbcr, VMM. 
t E. \V. Honrdsloy. Soptombcr. 100.', 
t John 11. Ci-Minir. .TjirniMrv. 1J)07. 



Pen Sharpeningr Arrangrement 

Fig. 48 shows a little arrangement that should prove very convenient 
in every drawing-room. This is a device used to facilitate the sharp- 
ening of drawling pens. A small wooden block, to which is attached 
a back, is all that is required. The stone is held in place by the left 
hand, and the pen, held by the thumb and forefinger of the right hand. 

Flff. 48. Pen Sbarpening Arranijreznent 

is moved backward and forward and at the same time given a rock- 
ing motion 80 as to grind all of the point. In this way first one and 
then the other nib of the pen are given an ideal finish. 

Tightening a Worn Thumb-nut 

When the adjusting nuts on bow instruments become worn out. they 
can be squeezed onto the screw in a visn as shown in Fip 49. and 

Vise jam 

Flff. 40. Tightening » Thumb-nut 

their useful life continued. This must be done very carefully or they 
will become too tight* 

• B. W. Ik'ardsloy. September. 100.'. 



Special Scales 

A very convenient scale for one-half and one-quarter siaee work may 
be made by fastening strips of paper with shellac varnish Just back of 
the graduations on a flat boxwood scale graduated full length witb 
sixteenths on one edge and thirty-seconds on the other. On these 
strips the divisions are marked and lettered, making the scale divi- 
sions equal eighths on the proportional scale, as shown in Fig. 50. 

iiiii II 






?»• 9^ :^ 



Pig. 60. Improvised Fractional 

Jlmtktuirt^. r. 

Pig. 61. Using a Machinist's Scale and Strips 
of Paper for Obtaining Fractional Scales 

Similarly a machinist's scale may be used by wrapping a strip of 
heavy paper lengthwise around the scale and fastening the two, with 
a screw at each end. on a beveled strip of wood, as shown in Pig. 51. 
With machinists' scales graduated to twentieths, twenty-fourths, twenty- 
eighths, etc., various odd proportions may be obtained.* 

Spacing Titles on Detail Work 
A drafting-room kink which is very useful as a time-saver in spac- 
ing titles on detail work consists of a few needles and a small piece 
of wood turned as is shown in Fig. 52. Through one end a narrow 





Tool for Spacing for Lettering on Drawings 

saw cut is made about one inch deep. In this cut are inserted and 
spaced as many needles as are desired. The needles are bound in 
place by two round-head wood screws. The cut shows such a spacer 
set to mark for two lines of letters.f 
" • K. wrBoardsloyT September. 1905. 

llaymond C. Williams. March, 1907. 


Ink Bottle Holders 

Ink bottle holders of various designs are constantly appearing in 
the technical press. In the following a number of the typical designs 
and suggestions are given, with a view of showing as many of the 
different designs as will satisfy all different requirements. 

Fig. 53 shows a bracket holder, which is attached to the under side 
of the table by a single screw so that it may be swung around out 
of the way. This arrangement insures that the Ink bottle is always in 

Jtackinerg, X Y. • 

Flfir. 63. Bracket-shaped Ink Bottle Holder 

the right place; it also eliminates the liability of blotting the work 
when filling the pen. The danger of spilling the ink is also reduced 
to the minimum.* 

A good and' substantial ink bottle holder is shown in Fig. 54. To 
make an ink bottle holder of this description, take a block of wood 
about 3% X 7 inches and 1% inch thick; have two holes bored in it part 
way. one at each end. to fit the ink bottles; also make a ^/(K-inch hole 
for the quill; this will be found very convenient when lettering. Make 
a cup-shaped hole at a convenient place to put tacks into, and on one 

* John Edgar. November, 1906. 



side make a groove about % inch wide to lay the lettering pens into; 
this completes the inkstand. It can be made at very small cost and 
presents a neat appearance.* 
The greatest efficiency, however, often lies in the greatest simplicity. 




t-- : 



..--- ^~.-Xr-t—%/-:-t^.. --4- - - - |-T-^ 

L + J 








Maehin»r]f, JV*. T. 

Fiff. 64. Ink Bottle Holder 

The illustration, Fig. 56, shows one of the most effective means of 
preventing what has always been a source of great annoyance to the 
draftsman, viz., the overturning of the ink bottle. In the center of a 

Mach in cry, a. T. 
Fig. 56. Layout on Piece of Paper for Making Ink Bottle Holder In Pig. 66 

four-inch square of ordinary drawing paper, scribe a circle equal to 
the diameter of the ink bottle. Divide the circle into about twenty- 
four parts as shown in Fig. 55, then, with a sharp knife, cut the paper 
from each of these twenty-four points to the center, following a radial 
line. Press the paper down over the nerk of the bottle. Around the 

• Peter Plantlnga. February, 1907. 


The device Illustrated may Beem to have a great many parts, as com- 
pared, for Instance, with a drawer, whlcb is the first thing one would 
think of for the purpose; but a drawer on this folding drawing table 
would have been In the way, and a slide of ample length would have 
required more depth than was here available. This holder is located 
at the left side ol the draftsman, and In the half-tone It is shown 
pulled out, affording ready access to either of the two Ink bottles 
which are locked fast In It, and requiring one hand only for removing 
the fllling quill. The bottles may be quickly removed for changing or 
renewing, by unscrewing the one tbumb-nut and removing the brass 
retalning-plate in Fig. 57, the back edge of which slips into the 
recess in the wooden strlii at the back. In the Improved design this 
wooden strip Is done away with, as Is evident In the line drawing, ears 
being formed on the plates B, Instead; also the thumb-nut and screw 

have been supersedod by a spring clip, C making It still easier 10 
remove the bottles. 

After Inking ilie pen, lifting the latch D with the tip of the finger 
enables the holder to be instantly pushed back out of the way; at the 
bock end of the strolic the latch drops into place again and the swing- 
ing holder Is retained there, entirely underneath the table and out of 
the nay. The construction should be clear from the drawings, the 
marks or symbols used being the same in Figs. SS and 59. The wooden 
parts of the holder arc glued together, other fastening being afforded 
by the wood screws and the rivets indicated In the assembly drawing. 
Fig. 5S. The portion of the drawing table to which the holder was 
attached is permanently horizontal, the drawing board, of variable slope, 
being pivoted above. Attachment was made by eight wood screws; 
Of course. If desired It could be all attached to a separate block, per- 
mitting, in the event of shipment, removal without disassembling.* 

• II. J. KennMly. Boptembcr, 100!J. 


To Prevent Lead PeDcll (torn Breaklnir 
Af small shell parti; filled with a piece of lead, steel, or shot, as 
1 In Fig. 60, and forced on the end of a drawing' pencil, mar 

Holder shown In Mb». 67 onfl OB 

appear to be a queer contrivance; but this end being ihe heaviest will 
naturally fall to the floor flrat and will prevent the lend from breaking.* 
To Remove Ink Lines iVom TracinK« 
Placer the part of the tracing, containing I he Itni.' lo be erased, upon 
Bome hard substance, stich as a celluloid Iriangle, and run over it 
ligbttr with a razor-ed^ed knife; this leaves the cloth In rallier a 

rougb condition, which wilt be readily taken hold of hy a medium hard 
eraser. Tbe tracing may then be smoothed down by using the rounded 
edge of ft knife handle or Its equivalent, and will then take the Ink 
wtUiout causing the latter to run.f 

L, 8epteint»r, 1B07. 



gmootblng' Wrinkled Blue-prints 

Fig. 61 shows a method of "iTonlns" soiled or wrinkled blue-p -ti 

after they are dry. The wrinkled print Is laid In a cabinet dr ii 

with Just enough of It outside to conveniently hold in the hands, i 

the drawer la tightly closed. After being pulled out, the print is 
perfectly smooth. The angle of pull should be adjusted to the Blrengtb 
of the paper. Pulling through once will, of course, cause the print 

to roll up, when released; If this is not desirable, and the print Is 
wanted to lie Hat, reverse the print, and pull through once more.' 
To Clean a TraciuK 
Tracings soon show the results of frequent use by becoming eoiled, 
which, while causing them to look bad. at the same time makes it 
Impossible to take good, nice, clear blue-t)rints from them. Oftentimes 
changes and corrections are "nencllcd In" on a tracing before inklni 

'llonard D. Yod 




a celluloid curve is used. By using a wooden curve, marks can be put 
on it to indicate the beginning and ending of the line desired, but doing 
this for some time puts the curve in a bad shape, and it becomes hard 
to discern which mark was put down last. It is hard to put marks 
on the rubber or celluloid curves, so the following method of using 
curves of any material seems to be far better. 

As can be seen in Fig. 63, there is a hole about 1/16 inch diameter 
put in each end of the curve. In use, the curve is laid on the drawing, 
the location of the holes marked with a pencil point, and the desired 
curve drawn. On the center line of the piece to be drawn, select two 
centers, as A and B. and from them locate the positions of the holes 
in the opposite side. Place the holes in the curve over these points 
and the curve is in the reversed position. The method is simple; in 
fact, it takes a much longer time to explain it than to follow it 

Graduated Curve for Drawing Symmetrical Lines 

Many ciirvos drawn by means of the so-called French curve, such as 
the ellipse, hyperbola and parabola, require that the same parts of the 

■ ■ — - r- 

9 10 11 yi I'i u 

Muc/iintrp, .V. i'. 

FlGr- 64. Draftsman's Graduated Curve 

French curve are used on each side of the axis of symmetry. The 
regularity of the curve and the degree of perfection of the symmetry 
will then depend on one's ability to reproduce in proper sequence on 
one side of the curve the parts of the curve used when previously draw- 
ing the other side. Fig. 64 shows a curve graduated on its edges with 
some arbitrary divisions, say in eighths. At every fourth one of these 
divisions a number is placed, starting with 1 at any convenient point 
on the curve and increasing by one until the graduations come back 
to the starting point. If the curve is made of celluloid the figures 
may be put on in black, so that when the curve is turned over with 
the figures down, they can bo seen readily. If the curve is made of 
an opaque substance the numbers must be put on both sides. The 
numbers on the back should exactly coincide with the numbers on the 
face, and should proceed around the curve in the same order. In the 
cut the graduations are not shown all around the edges of the curve, 
but in graduating a curve they should, of course, be carried all around. 

Attachment for Drawing Circles with Large Radii 

In laying out work, it is often necessary to locate a center or some 
other point beyond the scope of the average-sized drafting-board. Fig. 



65 illustrates a simple device that has been found to meet the require- 
ments when such occasion arises. If the attachment is made accord- 
ing to the dimensions given, it will fit any board up to 1^ inch in 


Draftiner-table Pencil-holder 

The pencil-holder shown in Fig. 66 may be made of either wood, or 
aluminum. A very pretty effect is secured by making it of Ms-inch 
strips of maple and cherry alternating. As an eight-degree tilt is a 




Maekinrr^, It. F, 

H'thu)*- SCKEW 
Pig. 66. A Handy Attachment for Dra^nin^ Circles with Large Radii 

convenient one for a table, this holder is made with the same angle 
80 as to keep the pencils from slipping out. By having sandpaper on 
the bottom, it can be used on a table that is considerably tilted by 
turning it around and having the cleat down. Nearly all draftsmen are 







Vi r 


JlTocAiiury, K. T 

Fig. QQ. A Draftlnfir-table Pencil-holder 

subject to annoyances arising from having their pencils and pens scat- 
tered all over the table; this holder, as can readily be seen, will rem- 
edy ihat.f 

ReBtoring Over-exposed Blue-prints 

Dissolve a quarter pound of potassium bi-chromate (a reddish crys- 
tal) in a gallon of water, and place the solution in a tray beside the 
wash tank. If a print is over-exposed or "burned." it is first placed 
in this solution and then washed in clear water: in this way a print 

• W. L. Van Nprb. June. 190!). 
tE. O. Peterson. October. 1009. 


l8 seldom lost because of over-exposure. It is. of course, possible to 
80 burn a print that it caunot be bleached, but the ordinary burn of 
from two to ten times the required exposure, responds to the above 
treatment. The solution keeps indefinitely, if a few crystals and also 
V'ater are occasionally added when required.* 

Miscellanoous Hints for the Draftingr-room 

It is sometimes desired to mako a tracing of cuts from catalogues, 
books, etc.. and to do this without romovlng the page. Perhaps it is 
not well known that by wotting the edges of the starchy side of trac- 
ing cloth, and rubbing it on the page, it will adhere firmly enough so 
that the tracing can be ma<le on the dull side without much trouble. 

In drawing a number of eircles or arcs from the same center it is 
best to glue a small i)i(»ce of paper over the center to hold the point 
of the l<'g. This will obviate the likelihood of making an 
unsightly hole in the drawing paiier. The best way is to have a sup- 
ply of these "ceuters" on hand, which can be made from a piece of 
waste drawing i)ai)er. A thin eoating of glue is spread on the paper, 
and when dry it is ready for usi^; when needed, a small piece is cut 
off, moistened, and fastened to the drawing paper. It can be easily 
removed from the sheet with th<' blade of a penknife, and the little 
glue which remains on the paper can be rtMuoved by the application 
of a rubber ink eraser. 

It is a good plan when leaving a tracing on the board at night to 
remove all the tacrks from the drawing and tracing except the one 
which is in the center of the top edge and the one which is in the 
center of the bottom edge. This allows it to go and come and to be 
tightened readily in the morning. 

In spacing a lin** for screw tlireads, when it is desired to represent 
the V, the thn-ad gage furnishes tlie means as well as anything could; 
simply choose the pitcji and make the impressions. 

When lines on an outer circle arc to be drawn tangent to an inner 
circle, a cardboard disk is a good substitute for the eccentrolinead, 
and is as much better than a circle as is a pin put in the center for 
radiating lines, than a lead i)eiicil point. 

It is well to havi- a i)iece of bloiiing paper -x3 inches hung on the 
wall, for, when it is needed, it is wanted in a htirry, and this makes 
a convenient ])lace for ir. 

A small flat oil-<an with screw lop is very convenient to have among 
the draftsman's kit; if oil is used frequently on the screws and nuts 
of instruments they not only work better, but last much longer. 

Mlfllph \V. Icivis. (►.■t.ilHr. T,M»i». 










Third Edition— Revised and Enlarged 


The Drafting of Cams, by Louis Rouillion - - 8 

Cam Curves, by Arthur B. Babbitt and F. H. Sibley 18 

Notes on Cam Design and Cam Cutting, by James L. 

Dinnany 80 

Cutting Master Cams, by Herbert C. Barnes - 87 

Suggestions in Cam Making 42 

Copyrlfffat, 1911, The Industrial Preu. Publlthen of Machinery. 
49-(»6 Lafayette Street. New York City 







represent one-balf a reToluUon of the cam. At I draw the p«rp«ndlca- 
lar 7 equal to the extreme throw, tn this case 1.^ Inch. Aa the rise 
of the follower Is to be imUorm, thla acUan mar be ahown by a straight 
line connecting A and Q. Divide the line ± I Into any number of equal 
parts, say eight, and erect perpendiculars at the points of division. 
The point B win then represent on»4uarter rerolutlon of the cam, 
and the distance EM will represent the throw at that point. In the 
same way the distance C E represents the amount of throw at one- 
eighth revolution, the distance O O, the throw at three^Ighths revolu- 
tion, and BO on for the other perpendiculars. 

To lay out the cam curve, describe about X. Pig. 2, as center any 
seml-clrcle, aef. Divide this seml-clrcle Into the same number of 



equal parts Into which the line A I was divided. Connect these poinli 
of division with the center X, and extend the Hues Indeflnltely beyond 
the seml-clrcle. On x&, make bj equal to BJ, on Xc, make ck equal 
to OK, and bo on, extending each radius a distance equal to Um corre- 
sponding perpendicular in Fig. 1. Then through the points a, /, Ife, t, 
etc., draw a smooth curve. This curve Is one-half the required cam 
curve. By drawing a similar curve to the left of a the cam curve to 
completed. By rotating the cam about the center, X, the follower, JI, 
would he forced to rise, with uniform velocity, through a distance of 
1% Inch. During the second half of the revolution It would fall 
uniformly, by aid of gravity or a spring, to the initial point a. 


Alternative Metbod of Laying Out Cam Curve 
Another way of laying out the same cam curve is as follows: Draw 
any Bemt-clrcle, a si. Fig. 3, and extend the diameter on one side a 
distance iq equal to the required throw. Divide 'ig into any number 
of equal parts, as at b, c, d, etc.. and divide the semi-ctrcle by the samo 
number of radii equally distributed. With Z as center and a radlna 

equal to Zb describe an arc cutting Z} B.t j. With the same center 
and radius equal to J c describe an arc cutting X fc at k. Continue this 
process through the points d, e, f, etc., thus obtaining the points I, n, 
n, etc. The latter are points on the required curve. 

The ezcesiive friction of a pointed follower such as that shown at 
R necessitates the emplorment of a follower that will reduce tb« 


amount of friction to a minimum. A amall roller meeti thl> require- 
ment. I( « roller Is employed u a follower the problem of lajlnK out 
the cam curve becomes modified. A roller traveling along the currea 
■hown in Figs. 2 and 3 would not Impart to tbe follower-rod the deelred 
UDlform rise and fall. The variation would be but slight, ret sufDcient 
to merit coailderatton where accuracy is deelred. 
OamB with Boiler Followers 
Fig. i represents a heart-shaped cam of the same dimensions as in 
rigs. 2 and 3, but with a roller follower. It Is the path of the center 

of this roller that requires the first consideration, as the position of 
this center regulates the throw. Therefore, the position of the center 
of the roller at various intervals In the rotation of the cam must he 
determined. Thla may be done by adding to each of the distances 
J B. EC. LD, etc., In Fig. 1, the radlua of the roller, and thus obtaining 


three^ighths of the rerolutlon is ahown hj Joining K and JT, and tlie 
period of rest daring the last eighth rerolution is shown at F G. The 
line A L is equal to the radius of the roller, and hy drawing the lino 
LR parallel to AG, the distance of the center of the roller from the 
base circle may be taken directly for any radius of the cam. 

To lay out the cam from the diagram, draw any base circle l«9» 
Fig. 5, and divide it into the same number of equal parts into which 
the line A G is divided, viz., sixteen. Through these points of division 

^TTT^ . — ^ Machinem»y. F. 

Vig. 7. Cam with Follower having Line of Action Bccentrlc with Cam Axis 

draw radii and extend them indefinitely. Upon these radii take Ia = 
LAf mh=iMH, ni = NI, etc., thus determining the positions of the 
center of the roller at the various intervals. Sketch in the outline of 
the roller in its different positions, and draw curves tangent to these 

Une of Action of Follower Bcoentric with Cam Axis 

In the cams previously considered, the line of action of the follower 
passes through the center of the cam-shaft When the line of actton 



of the follower passes to either side of the center of the cam-shaft, as 
in Fig. 7, a different method of laying out the cam curve becomes 
necessary. Assume that the requirements and conditions are the same 
as in Fig. 2, excepting that the line of action of the follower shall be 
one inch to the right of the center of the cam-shaft. Draw the indefi- 
nite line XA passing through the center of the cam-shaft. One inch 
to the right of X draw the line of action A /, of the follower, perpen- 
dicular to XA. Let B be the lowest position that the follower is to 
assume, and let f be the highest. Divide the throw, B /. into any num- 
ber of equal parts, as at c, d and e. Through A describe a circle with 
X as center. Divide this circle into twice the number of equal parts 
into which B/ is divided. From each of these points /, K, L, etc., 
draw tangents to the circle. Then, with X as center, describe arcs 
through c. d, e, and /. Where the arc c cuts the tangents from points 


Flff. 8. Cam and FoUower both havlnir Variable Motion 

J and P, as at C and /, are points on the desired curve. Where the 
arc through d cuts the tangents from K and 0, as at D and H, are also 
points on the curve. The points E, F, and G are obtained in a like 

Cams with Pivoted Followers 

The problem in Fig. 2 may be further modified by having the follower 
pivoted instead of acting in a straight line. In this case, the line of 
action becomes the arc of a circle. Problems of this nature may be 
solved by substituting for the straight line of action shown at i q. Fig. 
3, an arc which shall represent the path of the follower. This arc of 
action takes the place of all the various radii in Fig. 3. and the points 
ft. c, d, etc., serve as a series of initial points from which to swing con- 
centric arcs to intersect the various positions of the arc of action of 
the follower. The method is analogous to that in Fig. 3. In Fig. 29 
this method is applied to a cam of un-uniform motion. 

of tbe toUower should correspond with tbe number ot dlvlsloDB Into 
wblch one revolution of the driver Is divided. The points B, C, D, etc.. 
of tile cam curve may be found by tbe method of intersections explained 
in Pig. 3. Tbls problem is of a general nature and is univera&llT 
applicable to problems Involving a disk driver and a follower otber 
than a flat-footed one. 

The "Flat-footed" Follower 
A tamlliar example of a flat-tooted follower 
and-lift mecbaniam used to actnate the engii 
steamers. The "lift" or "wiper" is pivoted u] 
is caused to oscillate b^ an eccentric placed 
abaft. In Fig. 9, let the arc througb which 
equal SO degrees — 45 degrees on either tide a 



tlie "toe" rise and fall with unitorm motion thnniRh 1^ Incli. It !■ 
required to design tbe npper (Me of the lift to give the desired throw. 
Divide the tbrow, A I, Into anr Dumber of egu&l psrts, aaj etght, 
KDd locate tbe center of the rock-sbaft, as Z. Upon a piece of tracing 
pi^er draw a quadrant, xhk, Ffg. 10, s ft being equal to onfrltalt tbe 
throw of the eccentric, say 8 inches. Draw cl at 45 degrees to a A, 
and k I at right angles to x ft. Through the point ot Intersection. 1, 
and with X as center, describe the arc 1 n. The arc ft h then repre- 
sents a quarter revolution of the eccentric, and the arc tM the corre- 
sponding angular movement of the rock-shaft crank. Divide tba arc 
ft h Into the same number of equal parts Into which the tbrow ot the 
toe was divided, vis., eight. Through these points of division dnw 
lines parallel to xm. Intersecting the arc « I In the points m, 0, p, etc. 
From these points draw radial lines. Now, while the eccentric Is 
moving through a quarter revolution with a unlfonn motion, as sbovn 


riB.lo. L>r.ou((C>rCaDi wnb "Flx-lboltd" Pollomr 

by the equal division of the arc h k, tbe center line of the 

crank will assume the correapondlng positions shown by the radial 


Place the tracing In Fig. 10 upon Fig. 9 eo that Z and x coincide, 
and the line cm falls upon the line Xil. Then draw upon the trac- 
Ing-paper the position of tbe line A. Rotate the tracing-paper about 
Z nntll mn coincides with ZM and draw the position of ths line B. 
Again rotate about X until x o coincides with X M and draw tbe post 
tlon ot tbe line C. Continue thU process until the positions oC tha 
lines D, B, F, stc. are located, A curve drawn tangent to the lines thus 
oUalnsd la the required cam cnrre. This latter procedure Is not shown 
tn tbe cuts. The use ot tracing-paper for Urlng out cam curves, as here 



exemplified, la applicable to the Ugring-out of a variety of such cunrea. 
The tracing may be made to assume diflCerent positions of either the 
driver or follower, and their relation shown at any desired interval 
during their action. 

In work dealing with cam curves there are some factors of a pra^ 
tical nature that must be considered, one of which may be here stated, 
as applying directly to the problem of the toe-and-lift. This factor is 
the easement of cam action to prevent Jerking. The action as drawn 
in Fig. 9 has too abrupt a beginning and ending, and should be modi- 
fled by an easement curve at both these points of action. In any action 
that tends to jerkiness, a smoother motion may be obtained by slightly 
modifying the curve at the offending point. 

Cams with Double Contact 

In the drawings of cams thus far shown, there has been but one 
point of contact between the driver and follower. Positive motion is 
often obtained by having two points of contact. Cams having two such 

Ftff. 11 

Flff. 12 

Flff. 13 

points of contact are subject to certain limitations. For instance, in 
Fig. 11, if A and B are two points of contact of the follower, and are 
a constant distance apart, and the curve A D B he any assumed curve 
of one-half revolution of the cam, the curve of the remaining half 
revolution is limited to a curve complementary to A D B. That is, the 
distances C F^ D O, and E H must equal the constant A B. 

If it is desired to have an independent movement throughout the 
entire revolution of the cam it will be necessary to have two cams 
placed one upon the other, one point of contact of the follower bear- 
ing upon the second cam. In this case, having assumed any curve for 
one of the cams, the other cam must be made complementary to the 
first, the constant distance apart of the points of contact forming the 
basis for the calculation. Forms of double contact cams are shown in 
Figs. 12 and 13. Fig. 12 is a rocker cam, and Fig. 13 is a tri-lobe cam 
giving three reciprocating motions to the follower for each revolution 

of the driver. 

Cylindrical Cams 

Fig. 14 illustrates a method for laying out cylindrical cams. Let 
(7 do be the plan, and Ha' the development of the cylinder shown 


In elevation at XA. Divide tbe plan Into anj number of equal parta 
at at a, b, c, etc., and project these points of division upon tbe front 
elevation of the cylinder as the elements A, B, 0, ate. On tlw deT«l- 
oped surface these elements appear as if, V, o*. etc. Upon the develoih 
ment, tar out the desired action, as In Figs. 1 and 6, avoldini or eaalnc 
all sharp comers. Suppose m I p to be such an action. This curve will 
then represent the path of the center of the follower. Let L Indicate 
the center of the follower. Then, as the cylinder Is rotated about Ita 
axle, the point L mores to and fro a distance L I, and with an Irrecn- 
lar motion dependent on the form of the curve mtp. The projection 
of this curve upon the elevation of the cylinder is shown at L m. 

The form of the roller-follower may be either cylindrical or conical; 
the question of the shape of the follower has been treated more com- 
pletely In Chapter V. In laying out the cam practically, the outline 
of the groove may be drawn by the method shown In Fig. 6, that Is, 

by drawing curves tangent to the various positions of the roller, and 
then, by winding the drawing about the metal cylinder blank, aar 
number of points of the groove may be located with a prlck-puneh; 
or, the drawing may be made directly upon the surface of the cylinder. 
The method for laying out a conical cam Is similar In principle to 
that for laying out a cylindrical cam, and la easily deduced from tba 

Laylnr Out a Cam tor Bhlfldnv Planer Belta 

■ The fallowing problem In machine design Is one of a series given to 
the students In mechanical engineering at Cornell University. It 
Alpiishes a good example of the method of reasoning applied to pra^ 
tleal problems in mechanics, and la also sn Interesting problem In 
qnlek-retom motions. The pnAlam calls for the designing ol a devlee 



for automatically shifting the belts of a planer. The driving shaft 
has a fixed pulley of wide fkce carrying two belts. The driven shaft 
has two sets of a loose and a fixed pulley. One set, smaller than the 
other, is driven by a crossed belt, and its shaft therefore rotates in 
a direction opposite to that of the driving shaft The larger fixed pul- 
ley drivef the planer while the tool is cutting, and the smaller fixed 


FIff. lA. Anmn^emaat for AatomaltioaMj Bhlftlnir PlAa«r B«lt0 

pulley causes a quick return of the tool while no work is being per- 

The shifter should be placed near the driven pulleys so as to operate 
each of the belts at its point of approach to its pulley, and to operate 
each belt separately. The shifter must also be operated automatically 
by the to-and-fro motion of the bed of the planer, and be capable of 



adjustment to allow for the variation of the momentum of the machine 
under different loads. 

In Fig. 15, A and B are the two loose pulleys of the driven shaft, 
and C and D the fixed pulleys. ^ is a grooved cam rotating about /, 
and having two roller followers F and G. if is a link driven to and 
fro by a tripping device attached to the planer bed. L, the shiftararm 
for the smaller pulleys, is a crank rotated by the follower F about Jf 
as a center. In a similar way, the crank N rotates about 0. The 
pivots J, M and O are carried on a plate made fast to the planer and 
not shown in the drawing. The portions of the cam to the left of F 
and to the right of O are arcs of circles with / as a center, and thera- 


Fig. 10. lAy-Ottt of Cam Cunre fbr Cam In Flir- 10 

fore, while either of the followers is traveling through these 
there will be no movement of the shifter-arms. The throw of either 
of the arms is occasioned by its follower traversing the irregular path 
between F and G. 

Imagine the link H drawn downwards. The cam then rotates 
towards the right about the center J. The follower F is held fixed In 
its position by the arc of the cam to its left, and therefore the 8hlft«r> 
arm L remains stationary. The path of the follower, Gf, however. Is 
through the irregular part of the cam between F and O, which causes 
it to rotate about as a center, thereby shifting the arm N from the 
loose pulley B to the fixed one D. If the link B is operated In the 
reverse direction to that Imagined above, the shifter^rm L will then 
beeome the active member, and the shifter-arm If will remain Inop- 


A method for determining the irregular path of the centers of the 
followers F and a is shown in Fig. 16. First locate the points M and 
from Fig. 15, and draw the circular arcs P and Q, the paths of the 
centers of the followers F and G. Then draw R and 8, the extreme 
positions of the center line of the shifter-arm L. Make angles T and 
U equal to the angle formed by the lines R and S. Divide the line 
through y W into six parts proportional to 1, 8, 5, 6, 8, 1, and through 
the points of division draw arcs with / as a center. Divide VX into 
six equal parts, throtigh which draw radial lines. The successive inter- 
sections of the circular arcs and the radial lines determine the paths 
of the followers F and G, bb WX, Lines drawn tangent to successive 
positions of a follower along the line W X will be the outline of the 
cam-slot at its irregular part. 

The slot Z, Fig. 15, permits adjustment of the link as called for in 
the conditions of the problem. The center of the opening for the belt 
in the shifter-arm L is placed nearer to the center line of the shaft to 
allow for the angularity of the cross belt. 

Laying Out an Intermittent Motion Cam with Pivoted Follower* 

The cam to be laid out is shown in Fig. 17. It turns toward the 
left and moves a 1-inch roller A which controls the lever B swinging 
on the stud C. The cam is to be keyed to a' shaft, together with sev- 
eral other cams, in all of which the keyway is at the beginning of 
thr cycle. The requirements which follow are selected to illustrate 
as simply as may be the method employed. The head of the lever B, 
which is 12% inches long, is to remain at rest until the cam has 
turned 150 degrees from the zero point or beginning of the cycle; it is 
then to advance 1% inch in 43 degrees; then it will dwell for 35 degrees 
more, and, finally, retreat 1^ inch in 92 degrees, after which it will 
dwell for the remainder of the cycle. In Fig. 17 it is seen that the 
roller A is located at one-third of the distance from the pivot of the 
lever to its head. Hence a movement of one-half inch is required of 
the roller in the cam to move the lever head 1^ inch. 

We will now begin the lay-out. Draw first the circumference of 
the cam; its diameter we will make 10 inches. With the keyway on the 
vertical diameter, draw a line through its center. With this line as 
zero, divide the circumference into 30-degree sections, as shown, and 
number them. Now draw the circle D with a radius of 4 3/16 inches, 
to show the extreme outer position of the center of the roller, and 
the circle E with a radius of 3 11/16 inches, to show the extreme 
inner position of the center of the roller. Next, with the center of 
the cam as its center, draw the circle F, so that it will pass through 
the center of the stud C, Beginning with the center of the stud C 
as zero, divide this circle into sections and number them, as shown, 
for each 60 degrees. Such further sub-divisions as may be needed later 
may be made when required. 

Proceed now with care to place the needle of a pair of good com- 
passes in the center of the roller A, and adjust them so that the pencil 

* Herbert C. Barnes, Machinxbt, October, 1008. 


point win paw through the center of the Btnd O. We will call thia 
ndlus R. Now haviiiK in mind the reQulrementa stated above, one 
being that the cam should turn 160 degreei from Its sera before the 
roller moves, place the end of the compaasee at 160 degrees on the 
circle D. Holding the needle here, with the radios A draw an arc 
Intersecting the stud circle F at the point O. It la seen that the 
point of Intersection Is at 60 degrees on the circle F. Now place the 
needle point 43 degrees further along on the stud circle, or at 108 d» 
grees, and with the radius R draw an arc Intersecting the circle S at 
the point H. The point H marks the halt of the advance of the roller. 

Fl,.17. layout 

and the beginning of Ka dwell. Now move the needle 35 degrees fur- 
tber along the stud circle to 13S degrees, and with the radius R draw 
another arc Intersecting the circle B at the point I. This point marks 
the end of the dwell and the beginning of Che retreat. Now move the 
needle 92 degrees further along the stud circle to 230 degreea and 
with the radius R draw an arc Intersecting the circle D at the point K, 
Thia point marks the end of the retreat and the beginning of the dwell 
for the remainder of the cycle. 

The {>olnU H. I and K being marked, draw radU through them ez- 
tadlog to the circumference of the cam circle. Knowing that the roller 
toCtna to advance at 150 degrees on the cam, the advance la seen to 


continue for 46 degrees. The roller then dwells for 35 degrees and 
retreats in 90 degrees, after which it dwells until the next advance 
hegins. It is proper that these figures do not agree with the figures 
for the leyer movement stated ahoye. Barring possible slight errors 
in the lay-out, thejr are correct for the cam. 

The radius of the inner wall of the raceway or groove is, of course, 
% inch less than that of the path of the cam center. Hence the radius 
of the inner wall of the outer dwell is 8 11/16 inches, and that of the 
inner dwell is 3 3/16 inches. This inner wall is the counterpart of the 
master cam which will be used for cutting the cam groove. 



When the curve of a cam is not determined by a given definite motion 
of the follower, and the condition presented to the designer is simply 
to make the follower move through a given distance during a given 
angle of motion of the cam-shaft, the ease and silence with which the 
cam works depends upon the character of curve used in laying out the 
advance and return. The uniform motion curve, the simplest of all 
curves to lay out, is a hard-working curve, and one that cannot be run 
at any great speed without a perceptible shock at the beginning and 
end of the stroke. 

Uniform Motion Curve 

The uniform motion curve would be represented in a diagram by 
the diagonal of the rectangle of which the base represents the angle 
of motion, and the altitude, the stroke of the cam, as shown by the 
full lines in Fig. 18. However, should the nature of the design demand 
a uniform motion for a given part of the revolution of the cam-shaft, 
the shock at beginning and end of stroke may be modified by increas- 
ing both the angle of motion and the stroke, and, in the diagram, 
filling in arcs of circles as shown by the dotted lines in Fig. 18. The 
amount of curvature at the ends of the stroke is dependent upon the 
amount it is possible to increase the angle of motion, and the centers 
of the arcs are determined by drawing perpendiculars to X Y as shown 
in Fig. 18. It will be noticed that the uniform motion has been main- 
tained for the original angle, the modifications at the ends causing 
the increase of angle of motion and of stroke, the rectangle formed 
by these two being shown by dotted lines. Even with these modificsr 
tions the cam is still apt to work hard, especially if the i^^le of 
motion is small. 

• IfACHiinaiT, AprU, 1907 ; July, 1907, and February, 1908. 


Harmonlo JtoUon Onrvw 
The crank or harmonic motion cum workg much more euUr than 
-the nnlform curre, and a cam laid ont with this motion may be nm 
at a high speed without much shock or nolae. To draw a diagram of 
tbla curre, draw a leml-clrGle having a diameter equal to tlie atroke 
of the cam, and divide thia semi-drcle and tlie line repreaenting Uie 
juigle of motion into the same number of equal parta. Tlie Interaao- 


lion of llnea drawn from these divlalona will give polnta on the cnrra. 
Fig. IB Bhows the harmonic curve and the manner in wlilch It la 

Qravlty Curve 

Probably the easleat working cam curve is the one known aa the 

.gravity curve. Thla curve has a constant acceleration or retardation 

■bearing the eame ratio to the speed aa the acceleration or retardation 
produced br pavltr; hence Ita name. A body falling from reat wUI 
.paai through about elxteen feet in one second (more accuiately 10.06 
feet). During the next aeoond the body will increase lU Telocity by 
-about thirty-two feet making the distance covered during the second 


Mcond fortr-filght rest; during eadi Bucceedlng second the body will 
Bstn In velocity thirty-two feet Using elxteen feet u a unit of 
meuurement. It will be seen that a body would trSTSl tbrougb units 
1, S, 5, 7, ft, etc., during succeaalTe seconds or units of time. To apply 
tbis motion to the cam carre, we might divide the angle of motion Into 
a given number of equal parts and, using the unite given above, we 
may increase tbe velocltj to a given maximum and then, retarding 
with the same ratio, bring the follower again to rest at the other end 
of the stroke. In the diagram, Fig. 20, the line representing the 
angle ot motion Is divided Into eleven equal parts which necessltsteA 

nc. ao. OAvitT uooou oum 
eleven dlvlslona on the line representing tbe stroke of the cam. If 
the motion for the first part of tbe stroke Is to have a constant accelera- 
tion, as referred to above, the distance traversed by the follower dur- 
ing the first part of the angle of motion would be one unit; In the 
second part, tbree unlta; In the third part, five units, and so on until 
tbe maximum velocity had been reached which would be during the 

Dlslancu iravprstd .Total ilistaace travetied 
Number i>f by follower durint' since bCKiDDiat! of 

11 1 61 

sixtb part of the angle of motion when the follower would travel 
through eleven units of motion. At this point the motion would begin 
to be retarded by a constant deduction which would cause tbe follower 
to move through nine units during the aeventh interval of time, seven 
units during the elgbtb. five units during the ninth, three units daring 


tbe tenth, and one unit during the eleventh and last interval. The sum 
of these units Is sixty-one, which will necessitate dividing the line 
representing the stroke of the cam Into elxty-one equal parts ot which 
the first, fourth, ninth, sixteenth, twenty-fifth, thlrty-slitb, forty-fifth, 
fifty-second, fifty-seventh, sixtieth, and sixty-first will be used for deter- 
mining points on the curve. The combination of the table given and 
the diagram shown in Fig, 20 will show how the gravity curve may 

Approximation of Gravity Curve 
A very close and satisfactory appro.Ylmatlon for the gravity curve, 
and one that entails less work than the theoretical, is shown in Fig. 21. 
The method of drawing is similar to the one used for the harmoDlc 
motion, excepting that an ellipse takes the place of the semi-circle. It 
can be seen very readily that the ratio of the major and minor asea 
will determine the character of the cam curve. To obtain a ctirve th«t 

will approximate the gravity curve, the line representing the stroke ot 
the cam should be used as the minor axis and the ratio of major azti 
to minor axis should be 1% to 1 or 11 to S. Dividing the seml-elllpse 
and line of angle of motion Into the same number of equal parts, and 
projecting, we obtain points on the curve. Fig. 22 Is given so that a 
comparison may be made of the three motions given above when applied 
to the same cam. 

Laying Out C&me for Kapld Motions 

As already mentioned In Chapter I, we may consider a cam mech- 
anism as being made up of two elements. Aa generally constructed, 
one element is a revolving plate cylinder, cone or sphere, and the other 
element Is a bar or & roller which has some form of reciprocating mo- 
tion. The revolving piece is usually made the driver, although the 
meclianlam may be made to work In the reverse order. The shape 
of a cam will depend upon the kind of motion that the follower is 
required to have. The motion of cams that are used for driving parts 



the points 8 and Tx and the intersections It, 2^, Z^ 2^, and 1'^, draw a 
smooth curve. This line will be a parabolic curre, reversing at Sj. 
The curve T, 8^ is constructed in the same way. Now wrap the sheet 
of paper ABDO around a cylinder whose circumference is equal to 
CD. The curve will take the position 8 T„ Fig. 27, and the curve TtSi 
will take a similar position on the reverse side of the cylinder. A 
groove made with these curves as center lines will drive a follower P 
up and down through the distance K, as the cylinder is rotated on its 
axis. The follower will start gradually at 8, attain its maximum 
velocity, and then come gradually to rest again at Tu the motion being 


Fiflr. 26. Accelerated Motion or Gravity 
Curve applied to Plate Cam 

Flff. 24. Unlfbrm Motion Cxirv'e 
■orlbed on Cylindrical Surflu:e 

uniformly accelerated and retarded. The sides of the groove are made 
parallel to 8 T^ and drawn to suit the diameter of follower P. 

Fig. 28 shows the distortion of the curve 8 T when the follower 
moves in the arc of a circle, with center at some point Q, instead of in 
a straight line. Points on the new curve are found by setting off from 
the intersections 6,. di. etc., the ordinates a 6 and cd. The curve 
fif Oi Cj T is then made the center line of a groove which will drive the 
hinged follower with the same variation in speed attained by the fol- 
lower in Fig. 27. 


Aooelemled Motion Pteta 0«m 

Fig. 25 sbowB how tba parabolic curre la applied to a plate cam. 

Tlie roller follower la luppoaed to oaclllate between P and P, aa tlie 

cam rotatea about 0. The curve P3^,' correapoDda to i9 Ti in Fls. S7, 

betng the center line of the parabolic groove In the lace at the plat*. 

Onljr one-bait of the cam la shown In the figure. Suppose thla cam la 
to rotate 180 degrees, while the follower movea from P to P,. Draw 
tbe baae circle with radtua P. the length of which will depend upon 
the size of the cam. Draw ± perpendicular to O P. and divide the 
arc subtended by P O A Into anr convenient number of parts, aar tbrM. 
Draw radU 01^ 02» etc. Divide PP, Into two equal parta at 9, and 
divide P9 Into the square of three parte, or 9. as shown. With as a 

center, and radius 01, And the Intersection i^ In the same war And 
tba otlier Intorssctlons Sn S^ otc, and draw a smooth curve ttarougta 
tbasa potnta. Tbla curve baa the same relation to the curve ot untform 

- on the Inside, be made the outline of the cam, then the follower will 

juabed up mechanically to P„ and allowed to tall by its own vetsht. 

~|]t remain In contact with the cam theoretically, because the prln- 

of uniformly accelerated motion Is the same as that of a falllnt 

In practice, however, the friction and the inertia of the c 

parts would probably prevent the follower from remaining In contact 
with the cam on its return motion If the oBcUlations were rapid. 

Fig. 30 abowB tbe parabolic cam constructed for a follower which 
moves in any curred path. The construction is the same aa in F*Ig. 25 
except that i>oints on tbe curre are located on radial linea Oa,, O&i, etc., 
(dEset from Ml by the distances 2a, = 4a. 3b, = 9b, and so on. 


Plata OAtn wltli Bar Follower 
When K plate cam Is to be laid out to drive a bar follower ttarougb 
ft certain CTCle ol operations, the conatructlon le more complicated. 
The baae circle la dlTlded aa In the prerlom case Into any convenient 
number of parta, and tbe square of tbe number of such parts laid out 
from P to 9 and from 9 to P„ Fig. 29. If the bar la to oscillate abont 
as a center. It will take tbe positions Ql, g4, 09, etc. as the radU 
01, 02, 03, etc.. come to tbe position OF. The Intersections 1, S, 8, 
and so on, are found Just the same as In the previous cases. Now 
liutead of drawing tbe curve for tbe cam outline through these points, 
straight lines which represent tbe edge of tbe follower must be drawn 


I 1) 



through the points making the same angle with a given radius as the 
follower makes with OP when tbe radius In question Is In tbe position 
OP. For example, angle a equals angle a,. Now the csm outline Is a 
smooth curve drawn tangent to these straight Hues. If the bar fol- 
lower. Instead of being centered at Q, moves up and down parallel to 
Its first position, then all these angles are right angles. If the face of 
the bar Is eurred, then the csm outline must be dnwn tsngsnt to ths 



curves after they liave been properly located with respect to their 
several radii. 

In drawing cams like Fig. 29» the proper relAion between the diam- 
eter of the base circle and the distance PPt must be assumed. If the 
base circle is too small, the cam outline will not be tangent to the 
edge of the follower in all positions, and the latter will not have -uni- 
formly accelerated and retarded motion. There is a rolling and sliding 
contact between the cam and its follower in the case of Fig. 29. The 
rolling action tends to carry the point of contact outward to the right 
of OP, during the upward motion, and to bring it back towards OP 
during the downward motion. The point of contact x does not neces- 
sarily occur when Oxi, is perpendicular to Qx. 

Effect of Changing Location of Cam BoUer 

When the line of motion of a follower passes through the center of 
rotation of the cam and the angle of the curve causes it to work hard. 


Usfhhwy. S. T. 

Flff. 31. Cam Roller on Center Line of Cam 

the curve may be modified, and the same motion of follower obtained 
by placing the follower with its line of action parallel to its original 
position and not passing through the center of the cam. A condition 
may be assumed, as shown in Fig. 31. 

Here we have a cam, rotating in the direction indicated by the arrow 
A, whose duty it is to move the follower % inch in the direction indi- 
cated by the arrow B during a 30-degree angle of motion of the cam- 
shaft. The angle of the cam as presented to the follower at the begin- 
ning of the stroke would be 35 degrees, as determined by the tangent 
to the curve of the centers, as indicated on the drawing. After the 
follower had moved one-third of its distance, the angle presented would 
be 32 degrees, and when two-thirds of the travel had been made, the 
angle of the curve would be about 30 degrees. The angles given are 
for a curve which would give a uniform motion to the follower. Should 
the cam curve work hard at the required speed we would naturally 
make the cam of greater diameter, if possible, which would reduce the 



angle of the cam. as shown by the difference In the angles presented 
in Fig. 31, as we go out from the center of rotation. The design of the 
machine, however, might make this change impossible. If it was 
simply necessary to get the follower from the position shown to a 
point % inch distant in a 30-degree movement of the cam-shaft, with- 
out regard to its motion, a harmonic or gravity curve might be used 
which would cause the cam to work easier. However, this would be 
impossible should our design require a uniform, or some other equally 
hard motion. A third way in which the angle of the curve might be 
decreased would be to make the angle of motion of the cam-shaft 
greater. This, too, might be made impossible by the limitations of 
our design. 

Another way. and one not commonly used, consists in changing the 
location of the cam roller. In Fig. 32 all conditions are the same as 


Flff. 32. Cmu RoU«r placed above Center Line of Cam 

in Fig. 31. except the roller has been placed % inch above the line 
passing through the center of the cam. The center of the roller will 
now pass along the line LM, or parallel to the line of motion in Fig. 
31. The angle of the curve presented to the roller in this case is 26 
degrees, much less than the angle presented in Fig. 31, and the angle 
decreases as the roller moves away from the center of rotation. The 
advantage that may be gained by moving the cam roller may be readily 
seen by comparing the results given above. There is, of course, a 
limit to the distance the roller may be changed, for if placed too far 
away from the center line, the thrust in the direction at right angles 
to the direction of motion of the follower would be so great as to ofEset 
the advantage gained. 

E>ren without the aid of an illustration it may be seen that to place 
the cam roller on the other side of the center would cause the angle 
of the cam curve to increase, thus making conditions worse. The offset 
of the roller should be in the direction opposed to the direction of 
motion of the cam. 



It is strange that the processes and methods of cam cutting have 
not heen improved more rapidly than they have. Twenty-five years 
ago, cams and gears were on ahout an equal footing; that is to say, 
most of both were cast to as nearly the proper shape as possible, after 
which the working surfaces or teeth were smoothed up with a file, and 
then the holes and hubs were finished in the usual manner. Some 
cams of both plate and barrel forms were cut, with suitable attach- 
ments, in the same machine the gears were cut in. This was an old 
hand indexing machine, with an automatic feed composed of a weight 
hung on the pilot wheel. Since that time gear cutting machinery has 
been wonderfully developed. All sorts of styles and arrangements are 
on the market, meeting every demand, from that for a general purpose 
machine to highly specialized forms. When it comes to cam cutting 
machinery, however, while machinery builders have special tools for 
their own work, so far as the writer is aware, there is no tool regu- 
larly on the market for cutting cams. The cam has thus fallen behind 
the gear in the process of development. Machine designers and ma- 
chine users are liable to be a little suspicious of cams, anyway. Con- 
Biderable trouble is often taken to avoid the necessity for using them. 
This is due, however, as much to faulty design and faulty construction 
as to any inherent objections to this form of mechanical movement. 
It is here proposed to call attention to some of the points to be con- 
sidered in designing and producing satisfactory cams, with the thought 
of thereby doing something to justify a more extensive use of them. 

Faults in the Design of Cams 

We have all seeu cams that were the cause of a good deal of pro- 
fanity, in which the trouble could be traced to the designer or machin- 
ist, who laid out the curves on what might be termed "schedule time"; 
that is to say, he simply made sure of his starting and stopping points, 
neglecting all intermediate points so long as the movement got there 
and got back on time. This, he thought, would be all that was neces- 
sary, not taking into account the shock and jar caused by the sudden 
starting and stopping of heavy slides, levers, etc., at even moderate 
speeds. The temptation to do this is always strong, especially in the 
case of barrel cams, where it is so much easier to use the milling ma- 
chine (gearing it up for a spiral to meet the schedule requirements), 
than it would be to lay out and form a curve with a gradual starting 
of the motion and a gradual stopping. There is nothing worse for the 
life of a machine than to have it operated by cams cut by this **sched- 

• Macuinebt, August, 1907. 



Cuttingr Gftxns of Uniform Lead in the Miller 

When it comes to the cutting of cams, the shop man naturally turns 
to the milling machine. Many manufacturers of milling machines 
make attachments which may be used for cutting cams with formers. 
None, however, is provided with anything except hand feed. Another, 
and the greatest, objection to them is that if there is much work to 
be done, one of the most expensive machines in the shop is tied up, 
and there are few shops that have a surplus of this brand of machine 
tools. For an occasional or an experimental job, however, there is 
nothing better than the milling machine. As has been before remarked, 
curves with easy starting and stopping movements cannot be cut 






Miicfim*- j,S. r. 

Fig. 33. Cutting a Face Cam of Uniform Rate of Throw 

without formers on it, or on any other machine for that matter; but 
cams which require a constant rise, such as the feed cams of some 
machines, may be cut on it without the use of formers. With barrel 
cams the method is obvious, it only being necessary to gear the spiral 
head with the lead-screw to get the required lead, and then cut a 
groove of this pitch in the body with an end mill of the same diameter 
as the roll. 

For cutting plate cams for the same kind of motion, the arrange- 
ment shown in Fig. 33 may be used, if the machine happens to have a 
vertical spindle milling attachment and a spiral head. All that it ia 
necessary to provide in addition is the extension shaft shown, and 
the special'bearing or bracket for supporting it. These parts are used 


to bring tbe gplral head to tbe center of the Uble. Th« abaft Ib bored 
out at one end to fit tbe stnd of the spiral head (called tbe worm gew 
Btud in the tables); tbe other Is tnmed and keyed to lit tbe changtt 
gears. Tbe cams may be held in tbe regular chuck, or on a face-plate 
fitted to tbe head. Small ones may be held on an arbor fitted to the 
spindle, with large collars to bold them flnnlj, clamped with a nut 
and vasher, or by an expansion bushing la the case of large holes. 
If they have keyways In them, and more than one or two are to be 
made, It will be well to Bt a key In the arbor to help locate them. It 
1b neccBBary to eet the mill central with the spiral bead to obtain cor- 
rect results, as the spiral will vary If this is not done. Advantage m»y 
sometimes be taken of this when, with the regular change gears, then 
Is no spiral of tbe exact pltcb required, in which case tbe desired rlM 

can be obtained by setting tbe head off center. This, however, wQl 
not give a uniform spiral, bb the pitch will keep Increasing as it laavM 
tbe center of tbe cam. As cam drawings are generally laid out or 
divided in degrees, it will be found convenient to divide the cam blank 
by tbe same method, while held In the spiral bead. To do this, wa 
may revolve the Index crank through two holes In the IS-hole circle or 
three holes In the 27-hole circle, as many times as are neceBsary, each of 
these divisions giving exactly one degree. 

Ulllinir Uachlne AttacbmentB for CuttinB- Cams with a Former 

Elxamples of attachtu«nLs rigged up to suit special requirements ara 
shown la the cuta Figs. 34 and 35. To a shop with a rather limited 
equipment, an order came la for a lot of eight macbinea, which required 
•even caina OKch, most of which were of the plate type. As this clan 
of work was sew to tbe shop, there were no facilities for this part of 
tbe Job; as nsnal, ft was decided to do the work on the milling ma- 

An old planer viae was scraped up and refitted ao as to have the 


movable Jaw a nice eliding fit — the screw haTlng been removed, of 
course. To this Jaw was fitted and bolted the spiral head of the miller, 
Id Buch a way that Its spindle could be placed either at right angles, 
or parallel to the cutter, as the case reaulred for barrel or plate cams. 
Ad arbor was made, long enough to pass through the head, carrying 
the former on the back end and the cam blank on the front end. A 
nut threaded onti>the back end held the former against the end of the 
BplDdle, BO there was Qo danger of the arbors rattling loose, no matter 
how badlf the work and tool chattered. 

For plate cams, as shown In Fig. 34, the former was made the oppo- 
site hand to that of the cam required. The overhanging arm had a 
center line marked on It as shown, which was matched with one on 
the frame so as to locate the arbor support central with the splndle- 
In the place of the arbor-supporting center there was fitted a stud 

with a roller of the same diameter as the cutter. The arm was held 
secure]^ by the regular milling machine braces, which are not shown 
In the cut. The method o( operation is obvious. The spiral head with 
its attached work and former was revolved, slowly, by hand. The 
action of the roller, held hy the overhanging arm In the groove o( the 
former, caused the head and nork to slldo back and forth on the ways 
of the planer vise, giving the proper movement between the work Bad 
the cutter to produce the desired contour of cam. The table was locked 
on the saddle. 

For barrel cams, the attachment was rearranged as shown in Fig. 85. 
The former roller was held firmly to a bracket bolted to the table of 
the machine. As the roller is on the opposite side of the milling 
cutter, the former and work are set ISO degrees apart on the work 
arbor, otherwise they are alike. The head 1b relocated on the movable 
vise Jaw to bring the axis of Kb spindle at right angles to the axis of 



Common Method of Making Master Came 

Assuming that the master cam has been properly machined and 
roughed down, -we will consider briefly the generally used method of 
finishing it This method comprises mounting the master cam in the 
dividing head of a universal milling machine, and gearing the head 
with the feed-screw of the table so that the table will advance in 
proper ratio with the turning of the work in the dividing head. In 
Fig. 37 a master cam is mounted as above described, and held against 
a cutter in the vertical spindle milling attachment on a milling ma- 
chine. This cutter is of the same diameter as the roll which will be 
used with the cam. The following description refers specifically to the 
cutting of the master cam for the cam shown in Chapter I, Fig. 17. 

The process is as follows: Feed the work against the cutter until 








Maehinery,y. Y. 

Fl|r. 87. Common Method of Milling Master Cams 

the cutter is 3 11/16 inches from the center of the master cam. Now, 
with the key-slot of the master cam which is the "zero" of the cam, 
directly In line with the cutter, turn the work 150 degrees. This 
finishes a part of the outer dwell of the cam. The next operation is 
to feed the worK agamst the cutter Vj inch while the dividing head 
turns 45 degrees. Since 45 degrees is % of 360 degrees, or one turn, 
we want gears which will turn the work V^ of a revolution while the 
table advances % inch. This is equal to one turn of the work while 
the table advances 4 inches. The gears on a feed-screw with four 
threads per inch, and 40-tooth worm-gear in the dividing head are: 

Gear on worm 36, Second gear on stud 2S, 

Gear on worm 36, Gear on screw 70. 

• UACunmmi, October, 1908. 



Having connected these gears with care, feed the work against the 
cutter 0.500 inch. The gears will at the same time turn the work 45 
degrees. This will give the advance of the cam. Now, with the table 
clamped where it is, turn the work 85 degrees further. This will give 
the inner dwell of the cam. Now change the gears so that the work 
will turn 90 degrees while the table is backed away ^ inch. This may 
be done by removing the first gear on the stud with 36 teeth and 
replacing it with a 72-tooth gear. Having done this with care to avoid 
disturbing the work during the change, back the work away from the 
cutter 0.500 inch. The gears will have turned the work 90 degrees 
more, the intermediate having been properly adjusted. This will give 



Fig. 38. Improved Method of Milling Master Cams 

the retreat of the cam. Now, with the table clamped where It is, turn 
the work until the cutter reaches the part already finished. 

The method which has Just been described, is very convenient when 
the change gears will give the combinations that are necessary, but it 
often happens that the desired combination cannot be made with 
even an approach to accuracy. This difficulty may be overcome, how- 
ever, by a method which is not in general use, but by which any de- 
sired result may be obtained. 

Improved Method for Producing Master Cams 

For convenience we will suppose that the master cam could not be 
cut with the gears named or with any others, in the vertical position. 




We will proceed as follows: Mount the roughed-out master cam as 
before in the dividing head, and place a 1-inch end mill in the vertical 
milling attachment, but, instead of setting them in a vertical position, 
incline each at an angle of 23 degrees 34 minutes, as shown in Fig. Ss. 
The reason for this will appear later. 

By inspection we see that if the work be fed against the cutter, 
Fig. 38, the. cutter will enter the work and approach the mandrel. We 
also see that if the angle of inclination be increased or reduced, the 



.V«i</i//i<rrj^..V. r. 
Fiff. 30. MiUlng a Maater Cam for a Drum Cam 

rate with which the cutter approaches the mandrel will vary likewise. 
A convenient combination of gears to use in this case is one which will 
turn the work 360 degrees while the table advances 10 inches. This 
result may be obtained by using four 36-tooth gears to turn the work. 
Having milled the master cam for the first 150 degrees to a radius 
of 3 11/16 inch as mentioned, we must find the correct distance to 
feed the table forward in order to make the cutter approach the man- 
drel % inch while the work turns 45 degrees. The computation is 
done as follows: Forty-five degrees is % of 360 degrees. Since the 
table is geared to advance 10 inches while the work turns 360 degrees, 
the table will advance y^ of 10 inches while the work turns 45 degrees. 
Thus the advance is 1% Inch to the 45-degree turn of the work. By 
inspection we see that in Fig. 38 the cutter and the work-face form 
two Bides in a right-angled triangle with a hypothenuse of ^ inch 



and one side of % inch. By solying, we find the angle a to be 28 
degrees 84 minutes, as before mentioned. Having now properly con- 
nected the gears to mill the advance on the cam, feed the table ahead 
1.250 inch. As Just stated, this will make the cutter approach the 
mandrel % inch while the gears will have turned the work 45 degrees. 
Now with the table clamped where it is, turn the work 35 degrees 
more. We are then ready to begin the retreat of the cam. We must 
arrange gears which will turn the work 90 degrees while the table is 
backed 1^ inch. By removing the 36-tooth gear from the screw and 
replacing it with a 72-tooth gear, we get this result. Carefully make 
the change so as not to disturb the work, and then back the table 1.260 
inch. The gears will have turned the work 90 degrees further. Now, 
with the table clamped where it is, turn the work until the master 
cam is completed. 

This system for making cams may be used only where uniform move* 
ments are required. While we have used It to entirely finish a master 
plate cam, any part of any cam requiring uniform motion may be 

Xachinery.y. Y. 
Ffff. 40. Special Finishing Cutter for Cam Grooves 

milled in this way with a degree of accuracy not readily obtained in 
any other way. In fact, the work should be as true as the machine 
on which it is done. The same system may be used to make a master 
cam for a drum cam, as shown in Fig. 39. Note, however, that the 
work is set 23 degrees 34 minutes from the vertical position, while 
the cutter inclines at right angles to, instead of parallel with, the axis 
of the mandrel. The same combinations of gears would be used if the 
drum cam action were similar to the one which we have discussed. 
The exceedingly low cost of making master cams by this method makes 
it profitable to provide a master cam for cutting the groove in a single 

Special Cutter for Finishing Grooved Cams 

A source of constant annoyance in milling grooves in cast Iron 
cams lies in the fact that finishing cutters quickly wear and become 
under size. They must then be laid aside or used for taking the rough- 
ing cuts, while a new cutter of full size is used for finishing. We will 
not discuss the practice of putting a piece of paper In the collet to 
make the small cutter run out of true. Another source of trouble, even 


with cutters with spiral flutes, is the tendency of the cutter to chatter, 
unless it is perfectly ground and all other conditions are exactly right 
Still a third trouble is in the tendency of the cutter to cut more on 
one side than on the other and to dig out stock in spots in the groove. 

In Fig. 40 is shown an extremely simple tool, the usefulness of 
which cannot be overestimated for finishing grooves in cast iron cams. 
It is a piece of tool steel, suitably machined to mount on an arbor. 
It is turned on the outside, with enough stock left on for grinding, 
after which the spiral grooves shown in the developed surface are 
milled with an angular cutter. The piece is then hardened and ground 
to size. The cam groove which we are to finish is roughed out from 
0.(K)2 inch to 0.012 Inch below size; the roughing cutter is removed 
from the spindle of the cam cutting machine, and this special tool is 
mounted in its place. The cam is then fed against the tool until the 
tool reaches the bottom, when the cam is turned one complete revo- 
lution. The tool will leave a true groove exactly the right size, and 
without chatter marks or hollows. 

By reason of the form of the cutting or scraping edges, it will outp 
last many ordinary cutters. Used in connection with it, a single 
roughing cutter may be repeatedly sharpened before it becomes too 
small for good results. 


actuates two rollers which are a certain fixed dlBtance apart trom 
each other. In order to avoid back-lash or eprlnelDg of the coonectlng- 
roda, a fault which 1b to be found In most cam presses, It is evident 
that the rollers must both touch the face of the cam at all times. In 
Fig. 47 1b shown the ordinary method of lading out such cams; thU 
cut also shows the fact that this ordinary method does not accomplish 
the end desired. We see that In this cam both curves which give to 
the slide Its up and down motion are constructed wtlh the same radii, 
which clearly must give a curve that is faulty at certain points. The 
one main feature that our cam must possess can be expressed as fol- 
lows: Two rollers of equal diameters, which are a certain flied dis- 

tance (i In Fig. 471 apart, on a line passing through center of cam. 
must always tangent the cam nhlle the cam makes its revolution. 
Turning to Fig. 47, we see that the curve which spans angle C and 
the dotted curve which spans angle D accomplish this object. A tittle 
reflection will convince one that this curve cannot be constructed abso- 
lutely correct by giving the radii for both the up stroke and down 
stroke curve, owing to the fact that the shape of one is entirely depen- 
dent on the shape of the other. 

We can, however, give the radii for one curve, and construct the 
other curve from It by the aid of the following device. It is assumed 
that In most cases it will be economical to cut a master cam, and use 
this for cutting the others. However, where only a few cams are to 
be cut, It will be well to construct one with the aid of our device, and 
use this one as a template for the others. Pig. 46 shows the device 
mentioned. First, cut the two arcs, A B and D C, which of course are 
perfect circular arcs of given radii, and also cut the curve AD from 
given radii. Then place center plug L Into center hole of cam and 
fasten bar F onto L. Bar F has two rollers, R and H. fastened In 
such a way that their center distance is equal to the center distance of 



other. If the motion were in a line with the axis of the cam, without 
any circular movement, conditions would be perfect in Fig. 48. It is 
evident that in intermediate conditions, the groove must be given a 
shape intermediate between the two. In many cams of this variety 
the heavy duty comes on a section of the cam which is of nearly even 
pitch and of considerable length. In such a case it is best to proportion 
the shape of the roll to work correctly during the important part of the 
cycle, letting it go as it will at other times. 

In Fig. 51, b is the circumferential distance on the surface of the 
cam, which includes the movement we desire to fit the roll to. The 



Flff. 61. Diagram Showing Method of Finding Shape of Cam Rolls 

throw of the cam for this circumferential movement is a. Line 00 
will then be a development of the movement of the cam roll during 
the given part of the cycle, and c is the movement corresponding to 5, 
but on a circle whose diameter is that of the cam at the bottom of 
the groove. With the same throw a as before, the line OV will be a 
development of the cam at the bottom of the groove. 017 then is the 
length of the helix traveled by the top of the roll, while OV is the 
amount of travel at the bottom of the groove. If then the top width 
and the bottom width of the groove be made proportional to OU and 
OV, the shape will be suitable to give the result we are seeking.* 

* R. E. Flanders, December, 1904. 





By H. P. Fairfield 
Third Edition 


Cutting Bevel Gears with a Rotary Cutter - - 3 
Making a Worm-Gear ...--- 17 
Spindle Construction -..._. 33 

CopyriKht, 1911, The InduRtrial PresA. Pubiishcrii uf Machinkky. 
49-S5 Lafayette Street. New York City 



plying this by the pitch, gives the number of teeth for which the cutter 
must be chosen, or sixty-four, approximately. In the table on the pre- 
vious page, a No. 2 cutter is listed to cut from 55 to 134 teeth, and is 
the one selected. When it is inconvenient to measure the back cone 
radius, use is made of the following formulas, taken from Brown k 
Sharpe Mfg. Co.'s catalogue (see Fig. 7 for notations) : 

Tano = 

No. of teeth for which 

to select cutter for gear ' 

No. of teeth for which _ 
to select cutter for pinion ' 

cos a 
sin a 

If the gears are miters, or alike, only one cutter is needed. 
is larger than the other two cutters may be needed. 




If one 

Setting-up the Work for Trial Cuts 

The cutting angle of the gear is 53 degrees 40 minutes, given from 
the center line of the gear, which corresponds to the center line of 


^ .-' 

Fig. 7. 

Na = No.o£ Teeth 
in Gear. 

Nb = Mo. of Teeth 
iit Pinion. 

a =■ Centi-t> Angle 
of Oear. 

MacktHtrp K- Y' 

Diagram Showingr Method of Selecting Cutters for Bevel Oears 

the Index centers. Tlie index head is therefore swiveled In the ver- 
tical plane to the position shown in Fig. 8, or through an arc of 53 
degrees 40 minutes by the graduations. The cutter is placed in cut- 
ting position upon the milling machine arbor, which must run true. 
Fig. 9 shows how the cutter and the index center are brought into 
alignment by adjusting the cross-slide. Most makes of cutters have 
a center line scribed on the tops of the teeth, or on the back face, to 
set the center to in making this adjustment. Be sure that the center 
runs true. It is best to try it with a test indicator. The gear blank, 
as shown in Fig. 10, is mounted firmly on a special true-running arbor, 
with a taper shank to fit the index head. 
Fig. 8 also shows the index pin and adjustable sector set for spacing 


In turning up the blanks, machine an extra one to use as a "dummy^ 
for setting the machine. This dummy may be used until cut up. 
Finally, settle upon a regular order of operations, follow it until a 
habit is formed, and fewer errors will result. 

As has been intimated, the method of cutting bevel gears just de- 
scribed, is only an approximate one. There is no possible way of 
cutting them to the theoretically perfect shape with formed milling 
cutters. There are probably more gears cut In the way we have 
described, however, than by any other method, as it requires the sim- 
plest outfit of tools, and can be done in any ordinary milling machine 
which Is provided with an indexing head. This method should not 
be used on large gears — especially those which are to run at a high 
rate of speed and transmit considerable power. Under these condi- 
tions, bevel gears cut with rotary cutters will be inefficient and noisy, 
and will be far from durable. For such service, the teeth should be 
planed by some one of the various machines made for the purpose, 
either by the templet or generating processes. 

There are so many gears cut with this method, however, that the 
ability to use it should be a part of the training of all machinists who 
class themselves as "all-around" workmen. 



the half-round drill or hog-nose drill, Fig. 60, and the special hollow 
drill, shown in Fig. 59. This last drill is used in a special drilling 
machine, as a rule, and not in ordinary lathe drilling. 

Where only a few spindles or shafts are to be drilled, the common 
twist drill, shown in Fig. 56, or the straight-fluted drill, shown in Fig, 
58 are used. As they are ordinarily made of much shorter lengths than 
the hole to be drilled is likely to be, some means must be used to 
lengthen them sufficiently to allow of the reach desired. This can be 
accomplished by first turning the shank end of the drill below sise. 
The stem or shaft to lengthen the drill can be a piece of cold rolled 
steel of the same diameter as the drill. A hole Is made in one end of 
this stem of a size that will closely fit the reduced shank of the drilL 
The turned down shank of the drill is then "tinned" with solder and 


M.T. 0. A M. ca 

LuUtttnal Plrm»,if T. 

Flff. 50. 


r\%. 57, 

ihtultrM, FtMt,it T. 

ImdMtriml PftU.S T. 

Pig. r>8. 

tndmttrial Pnu.S t. 
Flff. 59. 
Flgrs. 60 to 69. Tools Used In Spindle Boring 

some of the soldering acid is dropped into the hole in the stem. To 
put the two parts together, grasp the drill next to the reduced end 
with a pair of gas pipe pliers, and by holding the tinned end of the 
drill and the drilled end of the stem in a Bunsen flame, they can, 
when heated sufficiently to make the solder run, be forced together. 
When cool they will be capable of withstanding great stress. This 
process is termed in the shop "sweating in" a drill. 

Where the hole which is to be drilled is of such a depth relative to 
its diameter as to make the length of shaft or stem so great that it 
will be too slender to use when the hole is first started, several stems 
of varying lengths may be provided. The process of sweating on these 
stems is so simple that one stem when used to its depth can be unsol- 
dered and another and longer one sweated into its place. The holding 
of the drill in a hand vise or pipe pliers when soldering insures keep- 

- -c . 


tried at both A and B, If the error shown by the indicator is greater 
than the limit set for the job, a light cut with the boring tool and 
another light reaming may be necessary. If, however, the hole is only 
slightly out of true, the high side of the hole can be marked, and a 
light scraping with the finishing reamer upon that side will true it up. 
Not much stock must be removed in this way, as the result of scrap- 
ing upon one side only is to make the hole oval instead of round. 
When the hole has been bored and reamed very carefully, the bar will 
not usually run out on the first trial more than 0.001 inch in 10 inches, 
and a touch of scraping will put this error right. The inside boring 


FiflT- 71. Rowgrhlngr Taper Reamer 

tool shown held in the toolpost in Fig. 63 is the common forged tool, 
and its usual form is shown in Fig. 69. Where shallow holes are to 
be turned out this is a good tool and is cheaply made. The tool and 
holder shown in Fig. 68 are, however, a better form when much work 
is to be done. The bar that holds the tool can be revolved to bring 
the tool point into any desired relation to the hole. By the use of 
suitable bushings, bars of any diameter may be used, and the length 
of bar can be easily suited to the length of the hole it is to be used 
upon. This holder takes several shapes or forms in different shops, 
and is well worth its cost. When large holes are to be started in the 

lnUu*tri,il Priti 

Tig. TJ. 



_. -., lnUu*truil Pr*U 

Flff. <3, 

Figfs 72 nnd 73. nnlshinu Reamer nud Counterbore 

end of the spindle, a small drill may be used to drill a shallow hole. 
The shallow hole can then be turned concentric with an inside boring 
tool, as stated above, and finally enlarged to the diameter of the drill 
to be used by counterboring with the tool shown in Fig. 73. The teat 
or leader a is a nice fit in the smaller concentric hole, and leads the 
cutting edges straight with the center line. A depth sufficient to admit 
the sizing drill beyond its cutting edges is all that needs to be made 
with the counterbore. 

Taper reamers have a tendency to draw into the work when In use. 
To counteract the drawing-in action, it is common practice to cut a 


Uw mlndle br Xartei wdttaUM W tlw ■>■», m 
oTlgtiul tratb w tnmnd. tb^* Uffowi th« Uptnd t 
Una wltb th* tathc, and nsulte in a pooM^nimlDg Ui 
that can oolr >r aeddmt be rqdaead and na- trot.- 
DMthoda tar flnlahlss tha contar bola and tm anriH 
troa wtth «aeb othar, anjr dtangaa mada wlien aattl 
taalad and ratnedted at tha time at th«b occumnca. 

Tba vtndlea made by the above deacribed metho 
W-polnt carbon and ara unhardened. If greater wea 
daflrad In the spindle bearlngB tbaa euch eplndlt 
caiboB ataal !■ often used for the eplndle, and the 1 
caaahardaned. The casehardenlns 1b done Just bef 
and flttlnc, and Is from 1/8S Inch to 1/16 Inch deep, 
•ortaoM naed for the bearings. To accomplleh this, i 
alrad to retain loft are copper-plated before treating 
1 to harden. This copper-plating prevents the i 
[ compound upon these surfaceH, and the 
a&lT ata hardened. 

In grinding spindles with a long heyway In the a 
•tanaa a drill prees spindle, It fs usual to fit a strip < 
tba kajrwar, and then shape the wood to the clrcumfe 
dla. Whan grinding spindles it ia desirable to have 
ehlnea ao set as to have the workman between the t\ 
will have a coarser wheal mounted and will bring the 
iB 0.001 of an Inch of alia; they can then be finished 
Bachlne with a finer wheel, leaving a surface that does not need poltali- 
Ins. A feed of from one-quarter to tbree-elghths Inch per revolution 
should be maintained when grinding, and the spindle should be amply 
supported by back rests.